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 amino acid residues with a signal peptide of 27 residues. Bdb contains a well-conserved motif, Cys-X-X-Cys, which functions as the active center of disulfide oxidoreductases such as DsbA, protein disulfide isomerase, and thioredoxin. The deduced amino acid sequence showed significant homology with those of several bacterial thioredoxins. The bdb gene complemented the Escherichia coli dsbA mutation, restoring motility by means of flagellar and alkaline phosphatase activity. The Bdb protein 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.