Cellular Distribution of beta-Lactamase RP4 Is Mediated by an Outer Membrane Protease

Abstract

RP4 .beta.-lactamase extracted from the outer membrane of wild-type Escherichia coli can be resolved into several interconvertible forms that differ in their stabilities, substrate profiles and apparent MW. .beta.-Lactamase isolated from outer membrane of strains which lack a protease that is involved in the cleavage of colicins differs from the .beta.-lactamase of parental cells in substrate profile, apparent MW and the ability to interconvert. The cellular distribution of .beta.-lactamase also differs between wild-type and protease-deficient mutants. Both strains have equivalent amounts of .beta.-lactamase in their outer membranes; the parental strain also has considerable .beta.-lactamase in the cytoplasmic membrane while the mutant does not. The mutant contains only 30% of the parental level of enzyme in the periplasm. The reduced level of periplasmic enzyme is probably the result of a defect in processing of membrane-associated .beta.-lactamase. The .beta.-lactamase isolated from the mutant can be converted to forms resembling those found in the parent by incubation with extracts or outer membrane isolated from the parent.