ARTIFACTUAL PROCESSING OF PENICILLIN-BINDING PROTEINS 7 AND 1B BY THEOMPT PROTEASE OF ESCHERICHIA-COLI

Penicillin-binding proteins (PBPs) were visualized in strains of Esche richia coli that carried mutations in one or more of the following pro tease genes: tsp, degP, ptr, and ompT. In the absence of a functional ormpT gene, PBPs 1b alpha and 7 were not processed to the shortened fo rms 1b beta and 8, respectively. Cleavage of PBPs Ib alpha and 7 could be restored by introduction of a plasmid carrying the wild-type ompT gene. These PBPs were processed only after cell lysis or after membran e perturbation of whole cells by freeze-thaw, suggesting that the clea vage was a nonspecific artifact due to contact with OmpT, an outer mem brane protease, and that such processing was not biologically signific ant in vivo. The degradation of other PBPs during purification or stor age may also be effected by OmpT.