SEC63 Homolog (SEC63)

Yeast and human SEC63 share 25.6% amino acid identity. Western blot analysis detected SEC63 at an apparent molecular mass of 83 kD in HeLa cell extracts and dog pancreatic microsomes. Subcellular fractionation indicated the SEC63 is an integral ER membrane protein. Protease protection experiments indicated that both the N and C termini of canine Sec63 are oriented toward the cytosol, with the DnaJ domain contained within the ER lumen, suggesting that the first hydrophobic stretch does not traverse the ER membrane.Western blot analysis detected Sec63 in all bovine and rat tissues examined. Immunofluorescence analysis of human hepatoma cells indicated that SEC63 and SEC62 colocalized with endoplasmic reticulum proteins.