Penicillin-binding Proteins of the Stalk of Caulobacter crescentus

Abstract
Summary: Properties of stalks isolated from Caulobacter crescentus were studied. Isolated stalks possessed a density close to that of the cellular outer membrane, and contained a very low activity of succinate dehydrogenase. The protein patterns were similar to those of the outer membrane. These results suggest that the membrane component of the C. crescentus stalk comprises mainly outer membrane. The patterns of penicillin-binding proteins (PBPs) in isolated stalks were different from those of total cell envelopes. The stalks possessed neither PBP 1A nor PBP 3 which is localized in the inner membrane of growing cells. PBP X (mol. wt 93000) and PBP Y (mol. wt 85000), which are minor PBPs in the total cell envelope fraction were greatly enriched in the isolated stalks. A mecillinam-resistant, stalk-defective mutant, C. crescentus CB15 mcr-816, lacked both PBP X and PBP Y. It is concluded that PBP X and PBP Y are localized mainly in the stalk. Whether they are involved in the stalk development remains to be investigated.

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