Penicillin-binding protein 7 and its relationship to lysis of nongrowing Escherichia coli.

The characteristics and possible physiological role(s) of a 30-kilodalton low-molecular-size penicillin-binding protein (PBP), PBP 7, in Escherichia coli were investigated. The amount of penicillin required to half saturate PBP 7 was approximately 5 micrograms/ml, and this PBP bound 15% of the total penicillin bound to all PBPs with a deacylation rate of greater than 120 min. This PBP was distinguishable from E. coli PBPs 1 to 6 by the pattern of [3H]penicillin-labeled peptides generated by partial proteolysis. A unique feature of PBP 7 was its capacity to bind numerous members of penem class antibiotics at relatively low concentrations. A striking correlation existed in drugs between capability of lysing amino acid-starved (nongrowing) E. coli and binding to PBP 7. The findings suggest that PBP 7 is a new, physiologically significant target for beta-lactam antibiotics.