The pediocin AcH precursor is biologically active

The properties of the pediocin AcH precursor, prepediocin AcH, have been st udied to gain insight into how producer cells may protect themselves from t he activity of intracellular prebacteriocins. The native 62-amino-acid prec ursor and the 44-amino-acid mature species were expressed in Escherichia co il host strains that lack the leader peptide processing enzyme, PapD. Both forms inhibited the growth of the test bacterium Listeria innocua Lin11, in dicating that the native precursor is biologically active. The two species also were synthesized in the context of maltose-binding protein chimeric pr oteins to facilitate the measurement of their relative specific activities. The chimeric form of the precursor was similar to 80% as active as the chi meric mature species. Of relevance to cell protection and pediocin AcH prod uction, it was determined that the precursor is strongly susceptible to ina ctivation by reducing agents and to degradation by chymotrypsin and endogen ous E. coli proteases. Taken together, the results indicate that the activi ty of prepediocin AcH may have to be controlled prior to secretion to preve nt toxicity to the host. Perhaps producer cells avoid membrane damage by ma intaining the precursor in a reduced inactive state or by degrading molecul es whose secretion is delayed.