Physiological properties of penicillin-binding proteins in group A streptococci

We detected five major penicillin-binding proteins (PBPs) in group A streptococci by labeling either cell membrane preparations or live bacteria with tritiated penicillin. All PBPs appeared to be equally accessible to penicillin in vitro and in vivo. Individual PBPs differed in their rates of deacylation, and four of the five PBPs underwent rapid inactivation both in vivo and in vitro. At least two processes seemed to contribute to in vivo inactivation; these were (i) a penicillin-induced release of all five PBPs into the growth medium and (ii) degradation, as evidenced by the appearance of penicillin-labeled protein band of lower molecular weight and also by a gradual increase in material migrating with the same electrophoretic mobility as PBP 3. Inactivation of the PBPs was stimulated greatly by pretreatment of bacteria with gentamicin, cerulenin, or Triton X-100, whereas chloramphenicol, tetracycline, and lincomycin treatments had no such effect.