A NOVEL FUNCTION OF ESCHERICHIA-COLI CHAPERONE DNAJ - PROTEIN-DISULFIDE ISOMERASE

Molecular chaperones, protein-disulfide isomerases, and peptidyl proly l cis-trans isomerases assist protein folding in both prokaryotes and eukaryotes. The DnaJ protein of Escherichia coli and the DnaJ-like pro teins of eukaryotes are known as molecular chaperones and specific reg ulators of DnaK-like proteins and are involved in protein folding and renaturation after stress. In this study we show that DnaJ, like thior edoxin, protein-disulfide isomerase, and DsbA, possesses an active dit hiol/disulfide group and catalyzes protein disulfide formation (oxidat ive renaturation of reduced RNase), reduction (reduction of insulin di sulfides), and isomerization (refolding of randomly oxidized RNase). T hese results suggest that, in addition to its known function as a chap erone, DnaJ might be involved in controlling the redox state of cytopl asmic, membrane, or exported proteins.