Vacuolar Protein Sorting Associated Protein (VTA1)

VTA1 contains N- and C-terminal coiled-coil domains. The N-terminal region of SBP1 is rich in basic amino acids, whereas the C-terminal region is acidic. Immunofluorescence analysis of HeLa cells showed that endogenous human SBP1 localized to the cytosol.Expression of an ATPase-negative mouse Skd1 mutant in HeLa cells redirected endogenous SBP1 and SKD1 from the cytosol to an aberrant endosomal structure derived from early and late endosomes and lysosomes. In control HeLa cells, SKD1 existed as a monomer, and SBP1 formed an oligomer protein complex. The ATPase-negative Skd1 mutant formed large heterooligomers with endogenous SBP1 and SKD1 when expressed in HeLa cells, suggesting that the ATPase activity of SKD1 is required for disassembly of the SBP1/SKD1 complex.