C-TERMINAL TRUNCATION OF BOVINE PROTEIN DISULFIDE ISOMERASE INCREASES ITS ACTIVITY

Protein disulfide isomerase as usually purified by the method of Lambert and Freedman (Biochem. J., 1983, 213, 225-234) although appeared homogeneous by sodium dodecyl sulfatepolyacrylamide gel electrophoresis can be separated into two major components on a size-exclusion high performance liquid chromatography column or by polyacrylamide gel electrophoresis. These two components have the same N-terminal sequences but the C-terminal sequences are different, suggesting that one is the C-terminal slightly truncated protein. The shortened protein is more active in both the isomerase and the thiol-protein oxidoreductase activities. © 1992.