Transcytosis-associated protein (TAP)/p115 is a general fusion factor required for binding of vesicles to acceptor membranes.
Transcytosis-associated protein (TAP) is found on transytotic vesicles (TCVs) and is required for their fusion with the target membrane. We developed a cell-free assay capable of differentiating targeting/binding of TCVs to membrane from later fusion events. We found that TAP mediates stable association of TCVs with the target membrane. The sequence of rat liver TAP (959-amino acid open reading frame) encodes a protein that contains (i) an N-terminal region (amino acids 1-649), (ii) an internal region with several coiled-coil stretches (amino acids 650-930), and (iii) a C-terminal acidic region (amino acids 931-959). Comparisons between TAP and other sequences indicate that TAP is identical to p115, a protein involved in cis to medial Golgi transport, and homologous to Uso1p, a yeast protein involved in endoplasmic reticulum to Golgi transport. Our findings suggest that TAP/p115/Usop1 is a general factor acting within the secretory and endocytic pathways to bind transport vesicles prior to membrane fusion.
Department of Molecular Biology, Princeton University, NJ 08544.
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D000077614:Golgi Matrix Proteins; D007425:Intracellular Membranes / Q000378:metabolism*; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D051381:Rats; D029701:Saccharomyces cerevisiae Proteins; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D018076:DNA, Complementary; D005656:Fungal Proteins; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C086888:USO1 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C091580:vesicular transport factor p115; D000255:Adenosine Triphosphate