Folding in vitro and transport in vivo of pre-beta-lactamase are SecB independent.

Abstract

The rate of folding of the precursor of β-lactamase is not influenced by the presence of SecB under conditions in which GroEL/ES retards the folding. Wild-type β-lactamase and several mutants in the signal or the mature protein, affecting either transport or enzyme kinetics and probably folding, were examined for total expression, total enzymatic activity, and transported β-lactamase (in vivo resistance) in secB^- and secB⁺ strains. We conclude that there is no indication of any relevant interaction between SecB and pre-β-lactamase in vitro, nor did the secB^- mutation affect the transport of wild-type β-lactamase or any of the mutants in vivo. Thus, putative Escherichia coli'folding modulators'must be of limited specificity.