Rcat domain found in E3 ubiquitin-protein ligase ARI7 and similar proteins; This subfamily contains probable RBR-type E3 ubiquitin-protein ligases (EC 2.3.2.31) including Arabidopsis thaliana ARI5, ARI6, ARI7, and ARI8, as well as Dictyostelium discoideum RbrA (also called Ariadne-like ubiquitin ligase). They may function as part of E3 complexes, which accept ubiquitin from E2 ubiquitin-conjugating enzymes and then transfer it to substrates. RbrA may be required for normal cell-type proportioning and cell sorting during multicellular development, and is also necessary for spore cell viability. Members of this subfamily contain an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of ARI7-like proteins that are essential for RBR E3 ligase activity and adopt the same fold as the BRcat domain.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*
gi 1063705430 291 NSKPCPRCKRPIEKNQGCMHMTCTPPCKYEFCWLCLGAWMDHGERTGGFYACNRY 345
Cdd:cd22583     1 NTKPCPKCKRPIEKNQGCMHMTCSPPCKHEFCWLCLGPWSEHGERTGGFYACNRY 55

BRcat domain found in ankyrin repeat and IBR domain-containing protein 1 (ANKIB1) and similar proteins; ANKIB1 is an RBR-type E3 ubiquitin-protein ligase that may function as part of the E3 complex, which accepts ubiquitin from specific E2 ubiquitin-conjugating enzymes and then transfers it to substrates. It contains N-terminal ankyrin repeats, and an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the BRcat domain of ANKIB1 that adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1063705430 213 LRSYIEDNRKMKWCPAPGCDFAIDFVAG---SGNYDVSCLCSFSFCWNCTEEAHRPVDCSTVSKWILK 277
Cdd:cd20346     1 LRSYVEDNPNLKWCPAPGCGRAVELPGGgseEGSPEVDCGCGHSFCFNCGEEAHRPVDCETVKKWLKK 68

Rcat domain found in E3 ubiquitin-protein ligase ARI7 and similar proteins; This subfamily contains probable RBR-type E3 ubiquitin-protein ligases (EC 2.3.2.31) including Arabidopsis thaliana ARI5, ARI6, ARI7, and ARI8, as well as Dictyostelium discoideum RbrA (also called Ariadne-like ubiquitin ligase). They may function as part of E3 complexes, which accept ubiquitin from E2 ubiquitin-conjugating enzymes and then transfer it to substrates. RbrA may be required for normal cell-type proportioning and cell sorting during multicellular development, and is also necessary for spore cell viability. Members of this subfamily contain an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of ARI7-like proteins that are essential for RBR E3 ligase activity and adopt the same fold as the BRcat domain.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*
gi 1063705430 291 NSKPCPRCKRPIEKNQGCMHMTCTPPCKYEFCWLCLGAWMDHGERTGGFYACNRY 345
Cdd:cd22583     1 NTKPCPKCKRPIEKNQGCMHMTCSPPCKHEFCWLCLGPWSEHGERTGGFYACNRY 55

BRcat domain found in ankyrin repeat and IBR domain-containing protein 1 (ANKIB1) and similar proteins; ANKIB1 is an RBR-type E3 ubiquitin-protein ligase that may function as part of the E3 complex, which accepts ubiquitin from specific E2 ubiquitin-conjugating enzymes and then transfers it to substrates. It contains N-terminal ankyrin repeats, and an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the BRcat domain of ANKIB1 that adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1063705430 213 LRSYIEDNRKMKWCPAPGCDFAIDFVAG---SGNYDVSCLCSFSFCWNCTEEAHRPVDCSTVSKWILK 277
Cdd:cd20346     1 LRSYVEDNPNLKWCPAPGCGRAVELPGGgseEGSPEVDCGCGHSFCFNCGEEAHRPVDCETVKKWLKK 68

IBR domain, a half RING-finger domain; The IBR (In Between Ring fingers) domain is often found to occur between pairs of ring fingers (pfam00097). This domain has also been called the C6HC domain and DRIL (for double RING finger linked) domain. Proteins that contain two Ring fingers and an IBR domain (these proteins are also termed RBR family proteins) are thought to exist in all eukaryotic organizms. RBR family members play roles in protein quality control and can indirectly regulate transcription. Evidence suggests that RBR proteins are often parts of cullin-containing ubiquitin ligase complexes. The ubiquitin ligase Parkin is an RBR family protein whose mutations are involved in forms of familial Parkinson's disease.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1063705430 206 EKYNRYFLRSYIEDNRKMKWCPAPGCDFAIDFVAGSGN-YDVSCL-CSFSFCWNCTEEAHRPVDC 268
Cdd:pfam01485   1 EKYEKLLLKSYVESDPNLKWCPTPDCGYIIELTDGCSNtSHVTCSkCGHEFCFNCKEEWHEGLTC 65

IBR domain, a half RING-finger domain; The IBR (In Between Ring fingers) domain is often found to occur between pairs of ring fingers (pfam00097). This domain has also been called the C6HC domain and DRIL (for double RING finger linked) domain. Proteins that contain two Ring fingers and an IBR domain (these proteins are also termed RBR family proteins) are thought to exist in all eukaryotic organizms. RBR family members play roles in protein quality control and can indirectly regulate transcription. Evidence suggests that RBR proteins are often parts of cullin-containing ubiquitin ligase complexes. The ubiquitin ligase Parkin is an RBR family protein whose mutations are involved in forms of familial Parkinson's disease.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*
gi 1063705430 290 ANSKPCPR--CKRPIEKNQGCM---HMTCtPPCKYEFCWLCLGAW 329
Cdd:pfam01485  16 PNLKWCPTpdCGYIIELTDGCSntsHVTC-SKCGHEFCFNCKEEW 59

Rcat domain found in E3 ubiquitin-protein ligase ARI7 and similar proteins; This subfamily contains probable RBR-type E3 ubiquitin-protein ligases (EC 2.3.2.31) including Arabidopsis thaliana ARI5, ARI6, ARI7, and ARI8, as well as Dictyostelium discoideum RbrA (also called Ariadne-like ubiquitin ligase). They may function as part of E3 complexes, which accept ubiquitin from E2 ubiquitin-conjugating enzymes and then transfer it to substrates. RbrA may be required for normal cell-type proportioning and cell sorting during multicellular development, and is also necessary for spore cell viability. Members of this subfamily contain an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of ARI7-like proteins that are essential for RBR E3 ligase activity and adopt the same fold as the BRcat domain.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*
gi 1063705430 291 NSKPCPRCKRPIEKNQGCMHMTCTPPCKYEFCWLCLGAWMDHGERTGGFYACNRY 345
Cdd:cd22583     1 NTKPCPKCKRPIEKNQGCMHMTCSPPCKHEFCWLCLGPWSEHGERTGGFYACNRY 55

BRcat domain found in ankyrin repeat and IBR domain-containing protein 1 (ANKIB1) and similar proteins; ANKIB1 is an RBR-type E3 ubiquitin-protein ligase that may function as part of the E3 complex, which accepts ubiquitin from specific E2 ubiquitin-conjugating enzymes and then transfers it to substrates. It contains N-terminal ankyrin repeats, and an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the BRcat domain of ANKIB1 that adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1063705430 213 LRSYIEDNRKMKWCPAPGCDFAIDFVAG---SGNYDVSCLCSFSFCWNCTEEAHRPVDCSTVSKWILK 277
Cdd:cd20346     1 LRSYVEDNPNLKWCPAPGCGRAVELPGGgseEGSPEVDCGCGHSFCFNCGEEAHRPVDCETVKKWLKK 68

Rcat domain found in human homolog of Drosophila Ariadne (HHARI) and similar proteins; This subfamily includes Drosophila melanogaster protein ariadne-1 (ARI-1), and its eukaryotic homologs, such as HHARI. ARI-1 is a widely expressed Drosophila RING-finger protein that localizes mainly in the cytoplasm, and is required for neural development. It interacts with the ubiquitin-conjugating enzyme, UbcD10. HHARI is also called H7-AP2, monocyte protein 6 (MOP-6), protein ariadne-1 homolog, Ariadne RBR E3 ubiquitin protein ligase 1 (ARIH1), ariadne-1 (ARI-1), UbcH7-binding protein, UbcM4-interacting protein, or ubiquitin-conjugating enzyme E2-binding protein. It is an RBR-type E3 ubiquitin-protein ligase highly expressed in nuclei, where it is co-localized with nuclear bodies including Cajal, PML, and Lewy bodies. It interacts with the E2 conjugating enzymes UbcH7, UbcH8, UbcM4 and UbcD10 in human, mouse and fly, and modulates the ubiquitylation of substrate proteins including single-minded 2 (SIM2) and translation initiation factor 4E homologous protein (4EHP). It functions as a potent mediator of DNA damage-induced translation arrest, which protects stem and cancer cells against genotoxic stress by initiating a 4EHP-mediated mRNA translation arrest. HHARI contains an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of HHARI and similar proteins that are essential for RBR E3 ligase activity and adopts the same fold as the BRcat domain.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1063705430 287 WILANSKPCPRCKRPIEKNQGCMHMTCTPP-CKYEFCWLCLGAWMDHGERtggFYACNRYE 346
Cdd:cd20356     1 WIAANTKECPKCHVTIEKNGGCNHMVCRNQnCKYEFCWVCLGPWEPHGSS---WYNCNRYD 58

Rcat domain found in two RING fingers and DRIL [double RING finger linked] 1 (TRIAD1); TRIAD1, also called ariadne-2 (ARI-2), protein ariadne-2 homolog, Ariadne RBR E3 ubiquitin protein ligase 2 (ARIH2), or UbcM4-interacting protein 48, is an RBR-type E3 ubiquitin-protein ligase that catalyzes the formation of polyubiquitin chains linked via lysine-48 as well as lysine-63 residues. Its auto-ubiquitylation can be catalyzed by the E2 conjugating enzyme UBCH7. TRIAD1 has been implicated in hematopoiesis, specifically in myelopoiesis, as well as in embryogenesis. It functions as a regulator of endosomal transport, and is required for the proper function of multivesicular bodies. It also acts as a novel ubiquitination target for proteasome-dependent degradation by murine double minute 2 (MDM2). As a proapoptotic protein, TRIAD1 promotes p53 activation, and inhibits MDM2-mediated p53 ubiquitination and degradation. Furthermore, TRIAD1 can inhibit the ubiquitination and proteasomal degradation of growth factor independence 1 (Gfi1), a transcriptional repressor essential for the function and development of many different hematopoietic lineages. TRIAD1 contains an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of TRIAD1 that is essential for RBR E3 ligase activity and adopts the same fold as the BRcat domain.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*..
gi 1063705430 290 ANSKPCPRCKRPIEKNQGCMHMTCTpPCKYEFCWLCLGAWMDHGERTggfYACNRYE 346
Cdd:cd20360     1 AHTKDCPKCHVCIEKNGGCNHMQCS-KCKHEFCWMCLGDWKTHGSEY---YECSRYK 53

Rcat (required-for-catalysis) domain, part of the RBR (RING1-BRcat-Rcat) domain; The RBR family of RING-type E3 ligases are characterized by containing an RBR domain, which was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. It is composed of an extended RING domain (RING1) followed by an in-between RING (IBR) domain and the catalytic domain, which is structurally an IBR domain but is commonly designated RING2. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently, where the IBR and RING2 domains have been renamed as BRcat and Rcat domains, respectively. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. The Rcat domain contains the catalytic cysteine residue and ubiquitination activity. RBR family members play roles in protein quality control and can indirectly regulate transcription. Evidence suggests that RBR proteins are often parts of cullin-containing ubiquitin ligase complexes. This model corresponds to the Rcat domain that adopts the same fold as the BRcat domain.

                          10        20        30
                  ....*....|....*....|....*....|....*....
gi 1063705430 291 NSKPCPRCKRPIEKNQGCMHMTCTpPCKYEFCWLCLGAW 329
Cdd:cd20336     1 NTKKCPKCKVPIEKNGGCNHMTCS-RCGTEFCWLCGKPW 38

IBR domain, a half RING-finger domain; The IBR (In Between Ring fingers) domain is often found to occur between pairs of ring fingers (pfam00097). This domain has also been called the C6HC domain and DRIL (for double RING finger linked) domain. Proteins that contain two Ring fingers and an IBR domain (these proteins are also termed RBR family proteins) are thought to exist in all eukaryotic organizms. RBR family members play roles in protein quality control and can indirectly regulate transcription. Evidence suggests that RBR proteins are often parts of cullin-containing ubiquitin ligase complexes. The ubiquitin ligase Parkin is an RBR family protein whose mutations are involved in forms of familial Parkinson's disease.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1063705430 206 EKYNRYFLRSYIEDNRKMKWCPAPGCDFAIDFVAGSGN-YDVSCL-CSFSFCWNCTEEAHRPVDC 268
Cdd:pfam01485   1 EKYEKLLLKSYVESDPNLKWCPTPDCGYIIELTDGCSNtSHVTCSkCGHEFCFNCKEEWHEGLTC 65

RING finger, HC subclass, found in two RING fingers and DRIL [double RING finger linked] 1 (TRIAD1); TRIAD1, also known as ariadne-2 (ARI-2), protein ariadne-2 homolog, Ariadne RBR E3 ubiquitin protein ligase 2 (ARIH2), or UbcM4-interacting protein 48, is an RBR-type E3 ubiquitin-protein ligase that catalyzes the formation of polyubiquitin chains linked via lysine-48, as well as lysine-63 residues. Its auto-ubiquitylation can be catalyzed by the E2 conjugating enzyme UBCH7. TRIAD1 has been implicated in hematopoiesis, specifically in myelopoiesis, as well as in embryogenesis. It functions as a regulator of endosomal transport and is required for the proper function of multivesicular bodies. It also acts as a novel ubiquitination target for proteasome-dependent degradation by murine double minute 2 (MDM2). As a proapoptotic protein, TRIAD1 promotes p53 activation, and inhibits MDM2-mediated p53 ubiquitination and degradation. Furthermore, TRIAD1 can inhibit the ubiquitination and proteasomal degradation of growth factor independence 1 (Gfi1), a transcriptional repressor essential for the function and development of many different hematopoietic lineages. TRIAD1 contains an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been corrected as RING-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR (RING1-BRcat-Rcat) domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase function to facilitate the ubiquitination reaction. This model corresponds to the RING domain, a C3HC4-type RING-HC finger required for RBR-mediated ubiquitination.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|..
gi 1063705430 136 TCGICFDSYPPEKIASVSCGHPFCTTCWTGYISTTINDGPGClMLRCPDPSC 187
Cdd:cd16773     2 TCGVCCEDVPKDELFSLACGHYFCNDCWKQYLTVKIKDGVST-GIECMAPDC 52

Rcat domain found in cullin-9 (CUL-9) and similar proteins; CUL-9, also called UbcH7-associated protein 1 (H7-AP1), p53-associated parkin-like cytoplasmic protein, or PARC, is a cytoplasmic RBR-type E3 ubiquitin-protein ligase that function as a tumor suppressor and promotes p53-dependent apoptosis. It mediates the ubiquitination and degradation of cytosolic cytochrome c to promote survival in neurons and cancer cells. It is also a critical downstream effector of the 3M complex in the maintenance of microtubules and genome integrity. Moreover, CUL-9, together with CUL-7, forms homodimers and heterodimers, as well as some atypical cullin RING ligase complexes, which may exhibit ubiquitin ligase activity. CUL-9 contains a CPH domain (conserved in Cul7, PARC, and HERC2 proteins), a DOC (DOC1/APC10) domain, cullin homology domains linked with E3 ligase function, and a C-terminal RBR domain previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of CUL-9 that is essential for RBR E3 ligase activity and adopts the same fold as the BRcat domain.

                          10        20        30
                  ....*....|....*....|....*....|....*...
gi 1063705430 292 SKPCPRCKRPIEKNQGCMHMTCTpPCKYEFCWLCLGAW 329
Cdd:cd20359     7 SKRCPSCQAQIEKNEGCLHMTCA-KCNHGFCWRCLKPW 43

Rcat domain found in an uncharacterized subfamily of RBR proteins; This subfamily contains uncharacterized members of the RBR family, including Arabidopsis thaliana mutator-like transposase and hypothetical protein At2g19610/F3P11.21. The RBR family of RING-type E3 ligases are characterized by containing a RBR domain, which was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. It is composed of an extended RING domain (RING1) followed by an in-between RING (IBR) domain and the catalytic domain, which is structurally an IBR domain but is commonly designated RING2. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been corrected as RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently, where the IBR and RING2 domains have been renamed as BRcat and Rcat domains, respectively. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. RBR family members play roles in protein quality control and can indirectly regulate transcription. Evidence suggests that RBR proteins are often parts of cullin-containing ubiquitin ligase complexes. This model corresponds to the Rcat domain that is essential for RBR E3 ligase activity and adopts the same fold as the BRcat domain.

                          10        20        30
                  ....*....|....*....|....*....|...
gi 1063705430 293 KPCPRCKRPIEKNQGCMHMTCTppCKYEFCWLC 325
Cdd:cd22584     3 RRCPQCGHMVELSEGCNHMTCR--CGYEFCYLC 33

BRcat (benign-catalytic) and Rcat (required-for-catalysis) domains, part of the RBR (RING1-BRcat-Rcat) domain; The RBR family of RING-type E3 ligases are characterized by containing an RBR (RING1-BRcat-Rcat) domain, which was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. It is composed of an extended RING domain (RING1) followed by an in-between RING (IBR) domain and the catalytic domain, which is structurally an IBR domain but is commonly designated as RING2. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBRs has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis), where the IBR and RING2 domains have been renamed as BRcat and Rcat domains, respectively. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. The BRcat domain adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity. RBR family members play roles in protein quality control and can indirectly regulate transcription. Evidence suggests that RBR proteins are often parts of cullin-containing ubiquitin ligase complexes.

                          10        20        30
                  ....*....|....*....|....*....|....*...
gi 1063705430 291 NSKPCPRCKRPIEKNQGCMHMTCtPPCKYEFCWLCLGA 328
Cdd:cd14799     1 NTKWCPKCHFGFEKERGCMHATC-PQCRQEFCWRCKRQ 37

BRcat domain found in two RING fingers and DRIL [double RING finger linked] 1 (TRIAD1); TRIAD1, also called ariadne-2 (ARI-2), protein ariadne-2 homolog, Ariadne RBR E3 ubiquitin protein ligase 2 (ARIH2), or UbcM4-interacting protein 48, is an RBR-type E3 ubiquitin-protein ligase that catalyzes the formation of polyubiquitin chains linked via lysine-48 as well as lysine-63 residues. Its auto-ubiquitylation can be catalyzed by the E2 conjugating enzyme UBCH7. TRIAD1 has been implicated in hematopoiesis, specifically in myelopoiesis, as well as in embryogenesis. It functions as a regulator of endosomal transport, and is required for the proper function of multivesicular bodies. It also acts as a novel ubiquitination target for proteasome-dependent degradation by murine double minute 2 (MDM2). As a proapoptotic protein, TRIAD1 promotes p53 activation, and inhibits MDM2-mediated p53 ubiquitination and degradation. Furthermore, TRIAD1 can inhibit the ubiquitination and proteasomal degradation of growth factor independence 1 (Gfi1), a transcriptional repressor essential for the function and development of many different hematopoietic lineages. TRIAD1 contains an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the BRcat domain of TRIAD1 that adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1063705430 216 YIEDNRKMKWCPAPGCDFAIDFVAGSGNYDVSCLCSFSFCWNCTEEAHRPVDCSTVSKWILKNSAESENMN 286
Cdd:cd20344     2 YVKSHPQLRFCPGPDCPVVIRALEPKAKRVQCKRCKTSFCFKCGEDYHAPTDCETIKKWLTKCADDSETAN 72

RING finger, HC subclass, found in Saccharomyces cerevisiae translation termination inhibitor protein ITT1 and similar proteins; ITT1 is a protein that modulates the efficiency of translation termination, resulting in the readthrough of all three types of nonsense codons UAA, UAG and UGA. ITT1 contains a typical C3HC4-type RING-HC finger.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|..
gi 1063705430 136 TCGICFDSYPPEKIASVSCGHPFCTTCWTGYISTTINDGPgCLMLRCPDPSC 187
Cdd:cd23134     6 HCGICFEEKKGSDFIKLPCGHVFCRECLQDYYTIHIQEGE-VSSVKCPDPNC 56

Ariadne domain; This entry represents the Ariadne domain found in the Ariadne subfamily E3 ubiquitin ligase proteins. The C-terminal Ariadne domain adopts an elongated four-helix bundle consisting of an antiparallel arrangement of seven-to-ten-turn long helices. The Ariadne domain is straddled on one side by the IBR domain, and on the other by the RING2 domain. Notably, the Ariadne domain embraces the surface of RING2 containing the catalytic Cys357. The ariadne Domain Masks the HHARI Catalytic Cys357 and Inhibits Intrinsic E3 Activity.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1063705430 355 DETERRREMAKNSLERYTHYYERW-ASNQTSRQKA-MADLQQAQMQNLEKlsdkqctPESQLK-FileAWL-----QIIE 426
Cdd:pfam19422   2 EDREKKAERAKRDLYRYMHYHNRYkAHTDSFKLESkLKETIQEKISILEE-------RDSKLRdF---SWVtnglyRLFR 71

                          90       100       110       120       130       140
                  ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 1063705430 427 CRRVLKWTYAYGYYL-----------PEHEHAKRQFFEYLQGEAESGLERLHQCVEKDLVQF 477
Cdd:pfam19422  72 SRRVLSYSYPFAFYMfgdelfkdemtKEEREIKQNLFEDQQQQLEANVEKLSKFLEEPFDEY 133

Rcat domain found in the RING finger protein 19 (RNF19) subfamily; This subfamily includes RING finger protein RNF19A and RNF19B, which are transmembrane (TM) domain-containing RBR-type E3 ubiquitin-protein ligases. RNF19A, also called double ring-finger protein (Dorfin) or p38, localizes to the ubiquitylated inclusions in Parkinson's disease (PD), dementia with Lewy bodies (LBs), multiple system atrophy, and amyotrophic lateral sclerosis (ALS). It interacts with Psmc3, a protein component of the 19S regulatory cap of the 26S proteasome, and further participates in the ubiquitin-proteasome system in acrosome biogenesis, spermatid head shaping, and development of the head-tail coupling apparatus and tail. It modulates the ubiquitination and degradation of calcium-sensing receptor (CaR), which may contribute to a general mechanism for CaR quality control during biosynthesis. Moreover, RNF19A can also ubiquitylate mutant superoxide dismutase 1 (SOD1), the causative gene of familial ALS. It may associate with the endoplasmic reticulum-associated degradation (ERAD) pathway, which is related to the pathogenesis of neurodegenerative disorders, such as PD or Alzheimer's disease. It is also involved in the pathogenic process of PD and LB formation by ubiquitylation of synphilin-1. RNF19B, also called IBR domain-containing protein 3, or natural killer (NK) lytic-associated molecule (NKLAM), plays a role in controlling tumor dissemination and metastasis. It is involved in the cytolytic function of NK cells and cytotoxic T lymphocytes (CTLs). It interacts with ubiquitin conjugates UbcH7 and UbcH8, and ubiquitinates uridine kinase like-1 protein, targeting it for degradation. RNF19B is a novel component of macrophage phagosomes and plays a role in macrophage anti-bacterial activity. It functions as a novel modulator of macrophage inducible nitric oxide synthase (iNOS) expression. Both RNF19A and RNF19B contain an RBR domain followed by three TMs. The RBR domain was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of the RNF19 subfamily that is essential for RBR E3 ligase activity and adopts the same fold as the BRcat domain.

                          10        20        30
                  ....*....|....*....|....*....|....*.
gi 1063705430 293 KPCPRCKRPIEK-NQG-CMHMTCTPpCKYEFCWLCL 326
Cdd:cd20355     5 KPCPRCGALIIKmDDGsCNHMTCAV-CGAEFCWLCM 39

BRcat domain found in the RING finger protein 19 (RNF19) subfamily; This subfamily includes RING finger protein RNF19A and RNF19B, both of which are transmembrane (TM) domain-containing RBR-type E3 ubiquitin-protein ligases. RNF19A, also called double ring-finger protein (Dorfin), or p38, localizes to the ubiquitylated inclusions in Parkinson's disease (PD), dementia with Lewy bodies (LBs), multiple system atrophy, and amyotrophic lateral sclerosis (ALS). It interacts with Psmc3, a protein component of the 19S regulatory cap of the 26S proteasome, and further participates in the ubiquitin-proteasome system in acrosome biogenesis, spermatid head shaping, and development of the head-tail coupling apparatus and tail. It modulates the ubiquitination and degradation of Calcium-sensing receptor (CaR), which may contribute to a general mechanism for CaR quality control during biosynthesis. Moreover, RNF19A can also ubiquitylate mutant superoxide dismutase 1 (SOD1), the causative gene of familial ALS. It may associate with the endoplasmic reticulum-associated degradation (ERAD) pathway, which is related to the pathogenesis of neurodegenerative disorders, such as PD or Alzheimer's disease. It is also involved in the pathogenic process of PD and LB formation by ubiquitylation of synphilin-1. RNF19B, also called IBR domain-containing protein 3 or natural killer (NK) lytic-associated molecule (NKLAM), plays a role in controlling tumor dissemination and metastasis. It is involved in the cytolytic function of NK cells and cytotoxic T lymphocytes (CTLs). It interacts with ubiquitin conjugates UbcH7 and UbcH8, and ubiquitinates uridine kinase like-1 (URKL-1) protein, targeting it for degradation. Moreover, RNF19B is a novel component of macrophage phagosomes and plays a role in macrophage anti-bacterial activity. It functions as a novel modulator of macrophage inducible nitric oxide synthase (iNOS) expression. Both RNF19A and RNF19B contain an RBR domain followed by three TMs. The RBR domain was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the BRcat domain of the RNF19 subfamily that adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1063705430 206 EKYNRYFLRSYIEDNRKMKWCPAPGCDFAIdfVAGSGNY--DVSCL---CSFSFCWNCTEEAHRPVDCST 270
Cdd:cd20338     3 EKYEEFMLRRVLVRDPDARWCPAPDCGYAV--IATGCAScpKLTCQrpgCGTEFCYHCKQPWHPNQTCDA 70

Rcat domain found in RING finger protein 144B (RNF144B); RNF144B, also called PIR2, IBR domain-containing protein 2 (IBRDC2), or p53-inducible RING finger protein (p53RFP), is a transmembrane (TM) domain-containing RBR E3 ubiquitin-protein ligase that induces p53-dependent but caspase-independent apoptosis. It interacts with E2 ubiquitin-conjugating enzymes UbcH7 and UbcH8, but not with UbcH5. It is involved in ubiquitination and degradation of p21, a p53 downstream protein promoting growth arrest and antagonizing apoptosis, suggesting a role in switching a cell from p53-mediated growth arrest to apoptosis. Moreover, RNF144B regulates the levels of Bax, a pro-apoptotic protein from the Bcl-2 family, and protects cells from unprompted Bax activation and cell death. It also regulates epithelial homeostasis by mediating degradation of p21WAF1 and p63. RNF144B contains an RBR domain followed by a potential single-TM domain. The RBR domain was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of RNF144B that is essential for RBR E3 ligase activity and adopts the same fold as the BRcat domain.

                          10        20        30
                  ....*....|....*....|....*....|....
gi 1063705430 293 KPCPRCKRPIEKNQGCMHMTCTpPCKYEFCWLCL 326
Cdd:cd20369     7 KQCPVCRVYIERNEGCAQMMCK-NCKHTFCWYCL 39

IBR domain, a half RING-finger domain; The IBR (In Between Ring fingers) domain is often found to occur between pairs of ring fingers (pfam00097). This domain has also been called the C6HC domain and DRIL (for double RING finger linked) domain. Proteins that contain two Ring fingers and an IBR domain (these proteins are also termed RBR family proteins) are thought to exist in all eukaryotic organizms. RBR family members play roles in protein quality control and can indirectly regulate transcription. Evidence suggests that RBR proteins are often parts of cullin-containing ubiquitin ligase complexes. The ubiquitin ligase Parkin is an RBR family protein whose mutations are involved in forms of familial Parkinson's disease.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*
gi 1063705430 290 ANSKPCPR--CKRPIEKNQGCM---HMTCtPPCKYEFCWLCLGAW 329
Cdd:pfam01485  16 PNLKWCPTpdCGYIIELTDGCSntsHVTC-SKCGHEFCFNCKEEW 59

BRcat domain found in RING finger protein 19B (RNF19B); RNF19B, also called IBR domain-containing protein 3 or natural killer (NK) lytic-associated molecule (NKLAM), is a transmembrane (TM) domain-containing RBR-type E3 ubiquitin-protein ligase that plays a role in controlling tumor dissemination and metastasis. It is involved in the cytolytic function of NK cells and cytotoxic T lymphocytes (CTLs). It interacts with ubiquitin conjugates UbcH7 and UbcH8, and ubiquitinates uridine kinase like-1 (URKL-1) protein, targeting it for degradation. Moreover, RNF19B is a novel component of macrophage phagosomes and plays a role in macrophage anti-bacterial activity. It functions as a novel modulator of macrophage inducible nitric oxide synthase (iNOS) expression. RNF19B contains an RBR domain followed by three TMs. The RBR domain was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the BRcat domain of RNF19B that adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1063705430 206 EKYNRYFLRSYIEDNRKMKWCPAPGCDFAIDFVAGSGNYDVSCL---CSFSFCWNCTEEAHRPVDCST 270
Cdd:cd20363     3 HKYEEFMLRRYLASDPDCRWCPAPDCGYAVIAYGCASCPKLTCEregCQTEFCYHCKQIWHPNQTCDM 70

RING finger, HC subclass, found in Saccharomyces cerevisiae DNA repair protein RAD16, Schizosaccharomyces pombe rhp16, and similar proteins; Budding yeast RAD16, also known as ATP-dependent helicase RAD16, is encoded by a yeast excision repair gene homologous to the recombinational repair gene RAD54 and to the SNF2 gene involved in transcriptional activation. It is a component of the global genome repair (GGR) complex that promotes global genome nucleotide excision repair (GG-NER) by removing DNA damage from non-transcribing DNA. RAD16 is involved in differential repair of DNA after UV damage, and repairs preferentially the MAT-alpha locus compared with the HML-alpha locus. Fission yeast rhp16, also known as ATP-dependent helicase rhp16, is a RAD16 homolog. It is involved in GGR via nucleotide excision repair (NER), in conjunction with rhp7, after UV irradiation. Both RAD16 and rhp16 contain a C3HC4-type RING-HC finger, as well as a DEAD-like helicase domain and a helicase superfamily C-terminal domain.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|.
gi 1063705430 137 CGICFDsyPPEKIASVSCGHPFCTTCWTGYISTTINDGPGClmlrcpdPSC 187
Cdd:cd16567     3 CGICHE--EAEDPVVARCHHVFCRACVKEYIESAPGGKVTC-------PTC 44

RING finger, HC subclass, found in Arabidopsis thaliana protein CHROMATIN REMODELING 27 (CHR27) and similar proteins; CHR27, also called protein SNF2-RING-HELICASE-LIKE 1, is a probable helicase-like transcription factor involved in transcriptional gene silencing. It associates with SUVR2 and contributes to transcriptional gene silencing at RNA-directed DNA methylation (RdDM) target loci but also at RdDM-independent target loci. It may be involved in nucleosome positioning to form ordered nucleosome arrays on chromatin. It associates with SUVR2 and functions redundantly with FRG2. It is required for the efficient methylation of a broad range of RdDM target loci. CHR27 contains a typical C3HC4-type RING-HC finger.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|
gi 1063705430 137 CGICFDsyPPEKIASVSCGHPFCTTCWTGYISttiNDGPGCLMLRCpdPSCLAAVGHDMV 196
Cdd:cd23142     3 CPICND--PPEDAVVTLCGHVFCCECVFQYLS---SDRTCRQFNHC--PLCRQKLYLDDV 55

BRcat domain found in RING finger protein 19A (RNF19A); RNF19A, also called double ring-finger protein (Dorfin) or p38, is a transmembrane (TM) domain-containing RBR-type E3 ubiquitin-protein ligase that localizes to the ubiquitylated inclusions in Parkinson's disease (PD), dementia with Lewy bodies (LBs), multiple system atrophy, and amyotrophic lateral sclerosis (ALS). It interacts with Psmc3, a protein component of the 19S regulatory cap of the 26S proteasome, and further participates in the ubiquitin-proteasome system in acrosome biogenesis, spermatid head shaping, and development of the head-tail coupling apparatus and tail. It modulates the ubiquitination and degradation of Calcium-sensing receptor (CaR), which may contribute to a general mechanism for CaR quality control during biosynthesis. Moreover, RNF19A can also ubiquitylate mutant superoxide dismutase 1 (SOD1), the causative gene of familial ALS. It may associate with the endoplasmic reticulum-associated degradation (ERAD) pathway, which is related to the pathogenesis of neurodegenerative disorders, such as PD or Alzheimer's disease. It is also involved in the pathogenic process of PD and LB formation by ubiquitylation of synphilin-1. RNF19A contains an RBR domain followed by three TMs. The RBR domain was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the BRcat domain of RNF19A that adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1063705430 206 EKYNRYFLRSYIEDNRKMKWCPAPGCDFAIDFVAGSGNYDVSC---LCSFSFCWNCTEEAHRPVDC 268
Cdd:cd20362     9 EKYEEFMLRRWLVADPDCRWCPAPDCGYAVIAFGCASCPKLTCgreGCGTEFCYHCKQIWHPNQTC 74

Modified RING finger, HC subclass (C4C4-type), found in RNF144 proteins; This group includes RNF144A and RNF144B, both of which are transmembrane (TM) domain-containing RBR-type E3 ubiquitin-protein ligases. RNF144A, also known as UbcM4-interacting protein 4 (UIP4) or ubiquitin-conjugating enzyme 7-interacting protein 4, targets DNA-dependent protein kinase catalytic subunit (DNA-PKcs), and thus promote DNA damage-induced cell apoptosis. It is transcriptionally repressed by metastasis-associated protein 1 (MTA1) and inhibits MTA1-driven cancer cell migration and invasion. RNF144B, also known as PIR2, IBR domain-containing protein 2 (IBRDC2), or p53-inducible RING finger protein (p53RFP), induces p53-dependent but caspase-independent apoptosis. It interacts with E2 ubiquitin-conjugating enzymes UbcH7 and UbcH8, but not with UbcH5. It is involved in ubiquitination and degradation of p21, a p53 downstream protein promoting growth arrest and antagonizing apoptosis, suggesting a role in switching a cell from p53-mediated growth arrest to apoptosis. Moreover, RNF144B regulates the levels of Bax, a pro-apoptotic protein from the Bcl-2 family, and protects cells from unprompted Bax activation and cell death. It also regulates epithelial homeostasis by mediating degradation of p21WAF1 and p63. Both RNF144A and RNF144B contain an RBR domain followed by a potential single-TM domain. The RBR domain was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been corrected as RING-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR (RING1-BRcat-Rcat) domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase function to facilitate the ubiquitination reaction. This model corresponds to the RING domain, a C4C4-type RING finger whose overall folding is similar to that of the C3HC4-type RING-HC finger. It is required for RBR-mediated ubiquitination.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....
gi 1063705430 135 LTCGICFDSYPPEKIASV-SCGHPFCTTCWTGYISTTINDGPGcLMLRCPDPSC 187
Cdd:cd16632     1 ITCKLCLEEVPLREMYTLqSCGCIFCLQCLKQYVEVLIREGNV-SSITCPDAAC 53

Rcat domain found in HOIL-1-interacting protein (HOIP) and similar proteins; HOIP, also called RING finger protein 31 (RNF31) or zinc in-between-RING-finger ubiquitin-associated domain protein, together with HOIL-1 and SHARPIN, forms the E3-ligase complex (also known as linear-ubiquitin-chain assembly complex LUBAC) that regulates NF-kappaB activity and apoptosis. It also interacts with the atypical mammalian orphan receptor DAX-1, trigger DAX-1 ubiquitination and stabilization, and participate in repressing steroidogenic gene expression. HOIP contains three Npl4 zinc fingers, a central ubiquitin-associated (UBA) domain responsible for the interaction with the N-terminal ubiquitin-like domain (UBL) of HOIL-1L, an RBR domain, and a C-terminal linear chain determining domain (LDD). The RBR domain was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the Rcat domain of HOIP that is essential for RBR E3 ligase activity and adopts the same fold as the BRcat domain.

                          10        20        30
                  ....*....|....*....|....*....|..
gi 1063705430 295 CPRCK-RPIEKNQGCMHMTCTpPCKYEFCWLC 325
Cdd:cd20351    19 CPKCKfRYALAKGGCMHFTCT-QCRHEFCSGC 49