Interaction of β‐Lactam Antibiotics with Penicillin‐Binding Proteins from Bacillus megaterium

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Abstract
The binding properties of 25 β‐lactam antibiotics to Bacillus megaterium membranes have been studied. The affinities of the antibiotics for the penicillin‐binding proteins (PBPs) are also reported. We found that PBP 4 has the highest affinity for nearly all the antibiotics studied whereas PBP 5 has the lowest affinity. Both PBP 4 and PBP 5 appear to be dispensable for the maintenance of bacterial growth and survival and appear to be dd‐carboxypeptidases. Only the β‐lactam cefmetazol bound preferentially to PBP 5 and has been used to study the inhibition of dd‐carboxypeptidase.Comparative studies with β‐lactam that simultaneously result in (a) binding to PBPs 1 and 3, (b) inhibition of cell growth and (c) lysis, stressed the importance of PBPs 1 and 3 for cell growth and survival.