Mu homology domain (MHD) of adaptor protein (AP) coat protein I (COPI) delta subunit; COPI complex-coated vesicles function in the early secretory pathway. They mediate the retrograde transport from the Golgi to the ER, and intra-Golgi transport. COPI complex-coated vesicles consist of a small GTPase, ADP-ribosylation factor 1 (ARF1) and a heteroheptameric coatomer composed of two subcomplexes, F-COPI and B-COPI. ARF1 regulates COPI vesicle formation by recruiting the coatomer onto Golgi membranes to initiate its coat function. Coatomer complexes then bind cargo molecules and self-assemble to form spherical cages that yield COPI-coated vesicles. The heterotetrameric F-COPI subcomplex contains beta-, gamma-, delta-, and zeta-COP subunits, where beta- and gamma-COP subunits are related to the large AP subunits, and delta- and zeta-COP subunits are related to the medium and small AP subunits, respectively. Due to the sequence similarity to the AP complexes, the F-COPI subcomplex might play a role in the cargo-binding. The heterotrimeric B-COPI contains alpha-, beta-, and epsilon-COP subunits, which are not related to the adaptins. This subcomplex is thought to participate in the cage-forming and might serve a function similar to that of clathrin. This family corresponds to the mu homology domain of delta-subunit of COPI complex (delta-COP), which is distantly related to the C-terminal domain of mu chains among AP complexes. The delta-COP subunit appears tightly associated with the beta-COP subunit to confer its interaction with ARF1. In addition, both delta- and beta-COP subunits contribute to a common binding site for arginine (R)-based signals, which are sorting motifs conferring transient endoplasmic reticulum (ER) localization to unassembled subunits of multimeric membrane proteins.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720864679 272 ESVHMKIEEKITLTCGRDGGLQNMELHGMIMLRISDDKFGRIRLHVENEDKKGVQLQTHPNVDKKLFTAESLIGLKNPEK 351
Cdd:cd09254     1 EGVHITVEEKISATLSRDGGLESLEVKGTLSLRINDEELAHIKLQLANNSDKGFQFKTHPNVDKKLFTSDSVLGLKDPSK 80

                          90       100       110       120       130       140
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1720864679 352 SFPVNSDVGVLKWRLQTTEESFIPLTINCWPSESGNGCDVNIEYELQEDHLELNDVIITIPLPATDP 418
Cdd:cd09254    81 PFPVNDPVGVLKWRLQGSDESLLPLTINCWPSESGGGCDVTIEYELNRDDLELNDVVISIPLPSGDA 147

Mu homology domain (MHD) of adaptor protein (AP) coat protein I (COPI) delta subunit; COPI complex-coated vesicles function in the early secretory pathway. They mediate the retrograde transport from the Golgi to the ER, and intra-Golgi transport. COPI complex-coated vesicles consist of a small GTPase, ADP-ribosylation factor 1 (ARF1) and a heteroheptameric coatomer composed of two subcomplexes, F-COPI and B-COPI. ARF1 regulates COPI vesicle formation by recruiting the coatomer onto Golgi membranes to initiate its coat function. Coatomer complexes then bind cargo molecules and self-assemble to form spherical cages that yield COPI-coated vesicles. The heterotetrameric F-COPI subcomplex contains beta-, gamma-, delta-, and zeta-COP subunits, where beta- and gamma-COP subunits are related to the large AP subunits, and delta- and zeta-COP subunits are related to the medium and small AP subunits, respectively. Due to the sequence similarity to the AP complexes, the F-COPI subcomplex might play a role in the cargo-binding. The heterotrimeric B-COPI contains alpha-, beta-, and epsilon-COP subunits, which are not related to the adaptins. This subcomplex is thought to participate in the cage-forming and might serve a function similar to that of clathrin. This family corresponds to the mu homology domain of delta-subunit of COPI complex (delta-COP), which is distantly related to the C-terminal domain of mu chains among AP complexes. The delta-COP subunit appears tightly associated with the beta-COP subunit to confer its interaction with ARF1. In addition, both delta- and beta-COP subunits contribute to a common binding site for arginine (R)-based signals, which are sorting motifs conferring transient endoplasmic reticulum (ER) localization to unassembled subunits of multimeric membrane proteins.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720864679 272 ESVHMKIEEKITLTCGRDGGLQNMELHGMIMLRISDDKFGRIRLHVENEDKKGVQLQTHPNVDKKLFTAESLIGLKNPEK 351
Cdd:cd09254     1 EGVHITVEEKISATLSRDGGLESLEVKGTLSLRINDEELAHIKLQLANNSDKGFQFKTHPNVDKKLFTSDSVLGLKDPSK 80

                          90       100       110       120       130       140
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1720864679 352 SFPVNSDVGVLKWRLQTTEESFIPLTINCWPSESGNGCDVNIEYELQEDHLELNDVIITIPLPATDP 418
Cdd:cd09254    81 PFPVNDPVGVLKWRLQGSDESLLPLTINCWPSESGGGCDVTIEYELNRDDLELNDVVISIPLPSGDA 147

Mu homology domain (MHD) of adaptor protein (AP) coat protein I (COPI) delta subunit; COPI complex-coated vesicles function in the early secretory pathway. They mediate the retrograde transport from the Golgi to the ER, and intra-Golgi transport. COPI complex-coated vesicles consist of a small GTPase, ADP-ribosylation factor 1 (ARF1) and a heteroheptameric coatomer composed of two subcomplexes, F-COPI and B-COPI. ARF1 regulates COPI vesicle formation by recruiting the coatomer onto Golgi membranes to initiate its coat function. Coatomer complexes then bind cargo molecules and self-assemble to form spherical cages that yield COPI-coated vesicles. The heterotetrameric F-COPI subcomplex contains beta-, gamma-, delta-, and zeta-COP subunits, where beta- and gamma-COP subunits are related to the large AP subunits, and delta- and zeta-COP subunits are related to the medium and small AP subunits, respectively. Due to the sequence similarity to the AP complexes, the F-COPI subcomplex might play a role in the cargo-binding. The heterotrimeric B-COPI contains alpha-, beta-, and epsilon-COP subunits, which are not related to the adaptins. This subcomplex is thought to participate in the cage-forming and might serve a function similar to that of clathrin. This family corresponds to the mu homology domain of delta-subunit of COPI complex (delta-COP), which is distantly related to the C-terminal domain of mu chains among AP complexes. The delta-COP subunit appears tightly associated with the beta-COP subunit to confer its interaction with ARF1. In addition, both delta- and beta-COP subunits contribute to a common binding site for arginine (R)-based signals, which are sorting motifs conferring transient endoplasmic reticulum (ER) localization to unassembled subunits of multimeric membrane proteins.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720864679 272 ESVHMKIEEKITLTCGRDGGLQNMELHGMIMLRISDDKFGRIRLHVENEDKKGVQLQTHPNVDKKLFTAESLIGLKNPEK 351
Cdd:cd09254     1 EGVHITVEEKISATLSRDGGLESLEVKGTLSLRINDEELAHIKLQLANNSDKGFQFKTHPNVDKKLFTSDSVLGLKDPSK 80

                          90       100       110       120       130       140
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1720864679 352 SFPVNSDVGVLKWRLQTTEESFIPLTINCWPSESGNGCDVNIEYELQEDHLELNDVIITIPLPATDP 418
Cdd:cd09254    81 PFPVNDPVGVLKWRLQGSDESLLPLTINCWPSESGGGCDVTIEYELNRDDLELNDVVISIPLPSGDA 147

C-terminal domain of adaptor protein (AP) complexes medium mu subunits and its homologs (MHD); This family corresponds to the C-terminal domain of heterotetrameric AP complexes medium mu subunits and its homologs existing in monomeric stonins, delta-subunit of the heteroheptameric coat protein I (delta-COPI), a protein encoded by a pro-death gene referred as MuD (also known as MUDENG, mu-2 related death-inducing gene), an endocytic adaptor syp1, the mammalian FCH domain only proteins (FCHo1/2), SH3-containing GRB2-like protein 3-interacting protein 1 (SGIP1), and related proteins. AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. Stonins have been characterized as clathrin-dependent AP-2 mu chain related factors and may act as cargo-specific sorting adaptors in endocytosis. Coat protein complex I (COPI)-coated vesicles function in the early secretory pathway. They mediate the retrograde transport from the Golgi to the ER, and intra-Golgi transport. MuD is distantly related to the C-terminal domain of mu2 subunit of AP-2. It is able to induce cell death by itself and plays an important role in cell death in various tissues. Syp1 represents a novel type of endocytic adaptor protein that participates in endocytosis, promotes vesicle tabulation, and contributes to cell polarity and stress responses. It shares the same domain architecture with its two ubiquitously expressed mammalian counterparts, FCHo1/2, which represent key initial proteins ultimately controlling cellular nutrient uptake, receptor regulation, and synaptic vesicle retrieval. They bind specifically to the plasma membrane and recruit the scaffold proteins eps15 and intersectin, which subsequently engage the adaptor complex AP2 and clathrin, leading to coated vesicle formation. Another mammalian neuronal-specific protein SGIP1 does have a C-terminal MHD and has been classified into this family as well. It is an endophilin-interacting protein that plays an obligatory role in the regulation of energy homeostasis. It is also involved in clathrin-mediated endocytosis by interacting with phospholipids and eps15.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720864679 273 SVHMKIEEKITLTCGRDGGLQNMELHGMIMLRISDDKFGRIRLHVENED--KKGVQLQTHPNVDKKLFTAESLIGLKNPE 350
Cdd:cd07954     1 EVFLDVVEKVNLLISKDGSLLNSEVQGEIALKSFLSGMPEIRLGLNNPDvgIKLDDVSFHPCVRLKRFESERVISFIPPD 80

                          90       100       110       120       130       140
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1720864679 351 KSFPVNSDVGVLKWrlqtteeSFIPLTINCWPSESGNGCDVNIEYELQED-HLELNDVIITIPLP 414
Cdd:cd07954    81 GEFELMSYRTVEPW-------SILPITIFPVVSEEGSQLEVVITLKLSESlQLTAENVEVHIPLP 138

AP-1 complex subunit mu N-terminal domain; AP-1 complex mu subunit is part of the heterotetrameric adaptor protein (AP)-1 complex which consists of one large gamma-, one beta-, one mu-, and one sigma-subunit. AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. In the case of AP-1 the coat protein is clathrin. AP-1 binds the phospholipid PI(4)P which plays a role in its localisation to the trans-Golgi network (TGN)/endosome. The mu subunit is comprised of an N-terminal longin domain followed by a C-terminal domain which is involved in the binding of the Y-X-X-Phi sorting signal.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720864679  13 GKAIVSRQF---VEMTrtriegLLAAFPKLMN----TGKQHTFVETESVRYVYQPMEKLYMVLITTKNSNILEDLETLRL 85
Cdd:cd14835    10 GKVLISRNYrgdVPMS------VIEKFMPLLMekeeEGNLTPILTDGGVTYIYIKHNNLYLLAVTKKNANAAMVLSFLYK 83

                          90       100       110
                  ....*....|....*....|....*....|....*..
gi 1720864679  86 FSRVIPEYCRALEENEISEHcFDLIFA-FDEIVALGY 121
Cdd:cd14835    84 LVEVFKEYFKELEEESIRDN-FVIIYElLDEMMDFGY 119