Molecular cloning and characterization of mammalian homologues of vesicle-associated membrane protein-associated (VAMP-associated) proteins.

We have identified human and rat homologues of the VAMP-associated protein (VAP) of 33 kDa of Aplysia californica (aVAP-33), which we designated VAP-A, VAP-B, and VAP-C. Human VAP-A (hVAP-A) was found to be identical to the recently reported protein hVAP-33, with the exception of two amino acid residues. VAP-B contained a coiled-coil domain and a transmembrane domain (TMD). Human VAP-B (hVAP-B) was 46 and 60% homologous of the amino acid level to aVAP-33 and hVAP-A, respectively. Human VAP-C was a splicing variant of hVAP-B, lacking both the coiled-coil domain and the TMD. hVAP-B had VAMP-binding ability. Moreover, hVAP-A and hVAP-B associated with each other through their respective TMDs. These results suggest that complex formation by VAPs might be important in the trafficking of mammalian vesicle.