Five penicillin-binding components occur in Bacillus subtilis membranes.

Membranes of BaciZZus subtilis to which [14C]penicillin G had been bound were fractionated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Five labeled components were separated. These five components differed from each other in the rates at which they bound penicillins and cephalosporins by up to four orders of magnitude. The major penicillin-binding component, V, was identified as the D-alanine carboxypeptidase, whose activity is not vital for the cell. Three of the other components, in contrast, bound penicillins and cephalosporins at rates comparable to that of the penicillin killing site in this organism.