RING finger (Really Interesting New Gene) domain and U-box domain superfamily; The RING finger is a specialized type of Zn-finger of 40 to 60 residues that binds two atoms of zinc. It is defined by the "cross-brace" motif that chelates zinc atoms by eight amino acid residues, typically Cys or His, arranged in a characteristic spacing. Canonical RING motifs have been categorized into two major subclasses, RING-HC (C3HC4-type) and RING-H2 (C3H2C3-type), according to their Cys/His content. There are also many variants of RING fingers: some have different Cys/His patterns while some lack a single Cys or His residue at typical Zn ligand positions (the fourth or eighth zinc ligand is prevalently exchanged for an Asp, which can indeed chelate Zn in a RING finger as well). C4C4-, C3HC3D-, C2H2C4-, and C3HC5-type RING fingers are closely related to RING-HC fingers. In contrast, C4HC3- (RING-CH alias RINGv), C3H3C2-, C3H2C2D-, C3DHC3-, and C4HC2H-type RING fingers are more closely related to RING-H2 fingers. However, not all RING finger-containing proteins display regular RING finger features, and the RING finger family has turned out to be multifarious. The degenerate RING fingers of the Siz/PIAS RING (SP-RING) family proteins and sporulation protein RMD5, are characterized by lacking the second, fifth, and sixth Zn2+ ion-coordinating residues. They bind only one Zn2+ ion. On the other hand, the RING fingers of the human APC11 and RBX1 proteins can bind a third Zn atom since they harbor four additional Zn ligands. U-box is a modified form of the RING finger domain that lacks metal chelating Cys and His residues. It resembles the cross-brace RING structure consisting of three beta-sheets and a single alpha-helix, which would be stabilized by salt bridges instead of chelated metal ions. U-box proteins are widely distributed among eukaryotic organisms and show a higher prevalence in plants than in other organisms. RING finger/U-box-containing proteins are a group of diverse proteins with a variety of cellular functions, including oncogenesis, development, viral replication, signal transduction, the cell cycle and apoptosis. Many of them are ubiquitin-protein ligases (E3s) that serve as scaffolds for binding to ubiquitin-conjugating enzymes (E2s, also referred to as ubiquitin carrier proteins or UBCs) in close proximity to substrate proteins, which enable efficient transfer of ubiquitin from E2 to the substrates.

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                   ....*....|....*....|....*....|....*
gi 30697894    135 LELGCSCKNELALVHYACALKWFLNHGSTVCEICG 169
Cdd:smart00744  15 LVSPCRCKGSLKYVHQECLERWINESGNKTCEICK 49

The RING-variant domain is a C4HC3 zinc-finger like motif found in a number of cellular and viral proteins; Some of these proteins have been shown both in vivo and in vitro to have ubiquitin E3 ligase activity. The RING-variant domain is reminiscent of both the RING and the PHD domains and may represent an evolutionary intermediate. To describe this domain the term PHD/LAP domain has been used in the past. Extended description: The RING-variant (RINGv) domain contains a C4HC3 zinc-finger-like motif similar to the PHD domain, while some of the spacing between the Cys/His residues follow a pattern somewhat closer to that found in the RING domain. The RINGv domain, similar to the RING, PHD and LIM domains, is thought to bind two zinc ions co-ordinated by the highly conserved Cys and His residues. RING variant domain: C-x (2) -C-x(10-45)-C-x (1) -C-x (7) -H-x(2)-C-x(11-25)-C-x(2)-C As opposed to a PHD: C-x(1-2) -C-x (7-13)-C-x(2-4)-C-x(4-5)-H-x(2)-C-x(10-21)-C-x(2)-C Classical RING domain: C-x (2) -C-x (9-39)-C-x(1-3)-H-x(2-3)-C-x(2)-C-x(4-48) -C-x(2)-C

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                   ....*....|....*....|....*....|....*
gi 30697894    135 LELGCSCKNELALVHYACALKWFLNHGSTVCEICG 169
Cdd:smart00744  15 LVSPCRCKGSLKYVHQECLERWINESGNKTCEICK 49

Domain of unknown function (DUF4153); Members of this family are annotated as putative inner membrane proteins.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30697894   275 WAVEGTGILLATGLLTVTLVWLIAP--RVGKKTARSGLHILLGGLCALTIVI----FFRfvVLTRIR-YG--PARYWAIL 345
Cdd:pfam13687 214 YARRGFFQLLAVTLLNLAVILLALRfaPRDKKKDRTWLRILLGVLCLLTLVLvasaLYR--MWLYISaYGltELRVLVLW 291

                          90
                  ....*....|.
gi 30697894   346 FIFWFLVFGIW 356
Cdd:pfam13687 292 FMLWLGLVLLL 302

The RING-variant domain is a C4HC3 zinc-finger like motif found in a number of cellular and viral proteins; Some of these proteins have been shown both in vivo and in vitro to have ubiquitin E3 ligase activity. The RING-variant domain is reminiscent of both the RING and the PHD domains and may represent an evolutionary intermediate. To describe this domain the term PHD/LAP domain has been used in the past. Extended description: The RING-variant (RINGv) domain contains a C4HC3 zinc-finger-like motif similar to the PHD domain, while some of the spacing between the Cys/His residues follow a pattern somewhat closer to that found in the RING domain. The RINGv domain, similar to the RING, PHD and LIM domains, is thought to bind two zinc ions co-ordinated by the highly conserved Cys and His residues. RING variant domain: C-x (2) -C-x(10-45)-C-x (1) -C-x (7) -H-x(2)-C-x(11-25)-C-x(2)-C As opposed to a PHD: C-x(1-2) -C-x (7-13)-C-x(2-4)-C-x(4-5)-H-x(2)-C-x(10-21)-C-x(2)-C Classical RING domain: C-x (2) -C-x (9-39)-C-x(1-3)-H-x(2-3)-C-x(2)-C-x(4-48) -C-x(2)-C

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                   ....*....|....*....|....*....|....*
gi 30697894    135 LELGCSCKNELALVHYACALKWFLNHGSTVCEICG 169
Cdd:smart00744  15 LVSPCRCKGSLKYVHQECLERWINESGNKTCEICK 49

Domain of unknown function (DUF4153); Members of this family are annotated as putative inner membrane proteins.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 30697894   275 WAVEGTGILLATGLLTVTLVWLIAP--RVGKKTARSGLHILLGGLCALTIVI----FFRfvVLTRIR-YG--PARYWAIL 345
Cdd:pfam13687 214 YARRGFFQLLAVTLLNLAVILLALRfaPRDKKKDRTWLRILLGVLCLLTLVLvasaLYR--MWLYISaYGltELRVLVLW 291

                          90
                  ....*....|.
gi 30697894   346 FIFWFLVFGIW 356
Cdd:pfam13687 292 FMLWLGLVLLL 302

RING-CH finger, H2 subclass (C4HC3-type), found in membrane-associated RING finger proteins MARCH2, MARCH3, and similar proteins; MARCH2 and MARCH3 contain a C4HC3-type RING-CH finger, also known as vRING or RINGv, a variant of C3H2C3-type RING-H2 finger, in the N-terminal cytoplasmic region, two transmembrane domains in the middle region, and a PDZ-binding motif at the C-terminus. MARCH2 is a Golgi-localized, membrane-associated E3 ubiquitin-protein ligase that is involved in endosomal trafficking through the binding of syntaxin 6 (STX6). It is involved in the cystic fibrosis transmembrane conductance regulator (CFTR)-associated ligand (CAL)-mediated ubiquitination and lysosomal degradation of mature CFTR through the association with adaptor proteins CAL and STX6. It also reduces the surface expression of CD86 and the transferrin receptor TFRC and regulates cell surface carvedilol-bound beta2-adrenergic receptor (beta2ARs) expression. Moreover, MARCH2 interacts with and ubiquitinates PDZ domains polarity determining scaffold protein DLG1 through its PDZ-binding motif, suggesting it may function as a molecular bridge with ubiquitin ligase activity connecting endocytic tumor suppressor proteins such as syntaxins to DLG1. MARCH3 is an E3 ubiquitin-protein ligase that is broadly expressed at relatively high levels in spleen, colon, and lung. It is localized to early endosomes, binds to MARCH2 and syntaxin 6, and is involved in the regulation of vesicular trafficking and fusion of the transport vesicles in endosomes. Its E2 specificity significantly overlaps that of MARCH2.

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                ....*....|....*....|....*....|.
gi 30697894 139 CSCKNELALVHYACALKWFLNHGSTVCEICG 169
Cdd:cd16699  18 CECTGTLGLVHRSCLEQWLSSSNTNSCEICH 48

RING-CH finger, H2 subclass (C4HC3-type), found in membrane-associated RING-CH6 (MARCH6); MARCH6, also known as membrane-associated RING finger protein 6, membrane-associated RING-CH protein VI (MARCH-VI), RING finger protein 176 (RNF176), protein TEB-4, or Doa10 homolog, is an endoplasmic reticulum (ER)-localized E3 ubiquitin ligase that ubiquitinates ER-associated proteins with a cytoplasmic domain in a ubiquitin-conjugating enzyme 7 (UBC7)-dependent manner), such as Mps2, UBC6, and Ste6. It also regulates its own UBC7-mediated degradation. MARCH6 interacts with ubiquitin-specific protease USP19, which deubiquitinates and stabilizes MARCH6 and inhibits p97-dependent proteasomal degradation. It is also involved in the cholesterol synthesis pathway by controlling the degradation of squalene monooxygenase (SM), and affects 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMGCR). Furthermore, it may be a key regulator of thyroid hormone activation in a number of tissues, since it mediates the proteasomal degradation of type 2 iodothyronine deiodinase (D2). MARCH6 contains 14 transmembrane helices and a conserved N-terminal C4HC3-type RING-CH finger, also known as vRING or RINGv, a variant of C3H2C3-type RING-H2 finger, that catalyzes ubiquitin Lys48-specific ligation.

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                ....*....|....*....|....*....|...
gi 30697894 139 CSCKNELALVHYACALKWfLNH-GSTVCEICGH 170
Cdd:cd16702  19 CKCSGSIKYVHQECLLQW-LKHsRKEYCELCKH 50