Cloning and expression of the gene for a protein disulfide oxidoreductase from Azotobacter vinelandii: complementation of an Escherichia coli dsbA mutant strain.

The gene for a disulfide oxidoreductase was cloned and sequenced from Azotobacter vinelandii and termed the dsbA locus. The deduced amino acid sequence contains 214 residues with a potential 17-residue signaling sequence on the N-terminal end. This gives the mature protein a calculated molecular mass of 21 799 Da. The A. vinelandii DsbA protein contains the well-conserved motif of C-P-H-C, which is found in the catalytic site of other bacterial DsbA enzymes. The A. vinelandii dsbA gene was expressed in Escherichia coli and was found to be able to complement an E. coli dsbA mutant strain by restoring flagellar and alkaline phosphatase activities. A. vinelandii dsbA mutant strains were impossible to characterize because of the extreme deleterious effect of the mutation. Therefore, the in vivo role of A. vinelandii DsbA is unknown, but it may function to form disulfide bonds and/or be involved in cytochrome biogenesis.