CLONING AND CHARACTERIZATION OF THE GENE FOR A PROTEIN THIOL-DISULFIDE OXIDOREDUCTASE IN BACILLUS-BREVIS

The gene (bdb) for protein thiol-disulfide oxidoreductase cloned from Bacillus brevis was found to encode a polypeptide consisting of 117 am ino acid residues with a signal peptide of 27 residues, Bdb contains a well-conserved motif, Cys-X-X-Cys, which functions as the active cent er of disulfide oxidoreductases such as DsbA, protein disulfide isomer ase, and thioredoxin, The deduced amino acid sequence showed significa nt homology with those of several bacterial thioredoxins, The bdb gene complemented the Escherichia coli dsbA mutation, restoring motility b y means of flagellar and alkaline phosphatase activity, The Bdb protei n overproduced in B, brevis was enzymatically active in both reduction and oxidization of disulfide bonds in vitro. Immunoblotting indicated that Bdb could function at the periphery of the cell.