COPA (alpha-coat protein) is processed to produce Xenin. Xenin stimulates exocrine pancreatic secretion to affect small and large intestinal motility, and inhibits pentagastrin-stimulated secretion of acid. In the gut, Xenin interacts with the neurotensin receptor. Membrane and vesicular trafficking in the early secretory pathway are mediated by non-Clathrin COP (coat protein) I-coated vesicles. COPI-coated vesicles mediate retrograde transport from the Golgi back to the ER and intra-Golgi transport. The cytosolic precursor of the COPI coat, the heptameric coatomer complex, is composed of two subcomplexes. The first consists of the COPB, COPG, COPD and COPZ subunits (also known as b-, g-, d- and z-COP, respectively), which are distantly homologous to AP Clathrin adaptor subunits. The second consists of the COPA, b'-COP and COPE subunits (also known as a-COP, COPP and e-COP, respectively).
Function:
The coatomer protein complex, alpha subunit (COPA) is a cytosolic protein complex that binds to dilysine motifs and reversibly associates with Golgi non-clathrin-coated vesicles. This interaction mediates biosynthetic protein transport from the ER, via the Golgi up to the trans Golgi network. The coatomer complex is required for budding from Golgi membranes, and is essential for the retrograde Golgi-to-ER transport of dilysine-tagged proteins. In mammals, the coatomer can only be recruited by membranes associated to ADP-ribosylation factors, small GTP-binding proteins; the complex also influences the Golgi structural integrity, as well as the processing, activity, and endocytic recycling of LDL receptors.
Subunit:
Oligomeric complex that consists of at least the alpha, beta, beta', gamma, delta, epsilon and zeta subunits. Probably interacts with PEX11A. Interacts with SCYL1.
Subcellular Location:
Cytoplasm. Golgi apparatus membrane; Peripheral membrane protein; Cytoplasmic side. Cytoplasmic vesicle, COPI-coated vesicle membrane; Peripheral membrane protein; Cytoplasmic side. Note=The coatomer is cytoplasmic or polymerized on the cytoplasmic side of the Golgi, as well as on the vesicles/buds originating from it.
Xenin: Secreted.
Tissue Specificity:
Uniformly expressed in a wide range of adult and fetal tissues. Xenin is found in gastric, duodenal and jejunal mucosa. Circulates in the blood. Seems to be confined to specific endocrine cells.
Similarity:
Contains 6 WD repeats.
SWISS:
P53621
Gene ID:
1314
Database links:
Entrez Gene: 100126041 Cow
Entrez
Gene: 1314 Human
Entrez Gene: 12847 Mouse
Entrez Gene: 304978 Rat
Omim: 601924 Human
SwissProt: Q27954 Cow
SwissProt: P53621 Human
SwissProt: Q8CIE6 Mouse
Unigene: 162121 Human
Unigene: 685025 Human
Unigene: 30041 Mouse
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