Export and secretion of overproduced OmpA-beta-lactamase in Escherichia coli.

The export of beta-lactamase to the periplasm of Escherichia coli can be directed by the OmpA signal peptide in the secretion cloning vector pIN-III. The overproduction of the hybrid precursor specifically induces a delay in the onset of processing of newly synthesized polypeptide chains. However, when the processing starts, no alteration in the rate of cleavage itself is observed. Our results suggest that the temporal mode of processing (which reflects translocation) does not depend on the nature of the signal peptide but rather depends on the nature of the polypeptide chain exported.