Crystal structures of penicillin-binding protein D2 from : Structural basis for antibiotic specificity.

beta-Lactam antibiotics that inhibit penicillin-binding proteins (PBPs) have been widely used in the treatment of bacterial infections. However, the molecular basis underlying the different inhibitory potencies of beta-lactams against specific PBPs is not fully understood. Here, we present the crystal structures of penicillin-binding protein D2 (PBPD2) from Listeria monocytogenes, a Gram-positive foodborne bacterial pathogen that causes listeriosis in humans. The acylated structures in complex with four antibiotics (penicillin G, ampicillin, cefotaxime, and cefuroxime) revealed that the beta-lactam core structures were recognized by a common set of residues; however, the R1 side chains of each antibiotic participate in different interactions with PBPD2. In addition, the structural complementarities between the side chains of beta-lactams and the enzyme were found to be highly correlated with the relative reactivities of penam or cephem antibiotics against PBPD2. Our study provides the structural basis for the inhibition of PBPD2 by clinically important beta-lactam antibiotics that are commonly used in listeriosis treatment. Our findings imply that the modification of beta-lactam side chains based on structural complementarity could be useful for the development of potent inhibitors against beta-lactam-resistant PBPs.