PROTEIN-DISULFIDE ISOMERASE ACTIVITY OF ELONGATION-FACTOR EF-TU

EF-Tu is involved in the binding and transport of the appropriate codo n-specified aminoacyl-tRNA to the aminoacyl site of the ribosome. We a nd others have recently shown that the Escherichia coli EF-Tu, in addi tion to its acknowledged role in translation elongation, displays chap erone-like properties. We report here that EF-Tu, like thioredoxin, pr otein disufide isomerase, and DsbA, catalyzes protein disulfide format ion (oxidative renaturation of reduced RNase), reduction (reduction of insulin disulfides), and isomerization (refolding of randomly oxidize d RNase). In contrast with most protein disulfide isomerases which pos sess vicinal cysteines and form an intramolecular disulfide upon oxida tion, EF-Tu, which does not possess vicinal cysteines, forms intermole cular disulfides upon oxidation, resulting in the appearance of multim eric forms, (C) 1998 Academic Press.