Penicillin-binding protein 3 of Listeria monocytogenes as the primary lethal target for beta-lactams

Abstract

Penicillin-binding proteins (PBPs) of Listeria monocytogenes were detected by their ability to bind to [2,3-3H]benzylpenicillin. Five proteins with M,s of 95,000, 84,000, 80,000, 76,000, and 49,000 were detected. PBPs 1 to 4 had a high affinity for [2,3-3H]benzylpenicillin and were relatively scarce (80 to 150 molecules per cell). In contrast, PBP 5 was more abundant (600 molecules per cell) but had a low affinity for [2,3-3Hlbenzylpenicillin. L. monocytogenes has a relatively high natural resistance to cephalosporins. Competition experiments showed that cephalosporins bound very poorly to PBP 3 but were good inhibitors of PBPs 1, 2, and 4, which were completely blocked at concentrations well below the MIC. Analysis of a spontaneous imipenem-resistant mutant revealed that resistance was likely due to an altered PBP 3 with a reduced affinity for [2,3-3H]benzylpenicillin. These results suggest that PBP 3 is a primary lethal target for ,-lactams in L.monocytogenes.

Characterization of the Bifunctional Glycosyltransferase/Acyltransferase Penicillin-Binding Protein 4 of Listeria monocytogenes

“…The sensitivity of L. monocytogenes EGD/⌬lmo2229 to ␤-lactams and vancomycin was similar to that of the wild type. The results show that PBP4 does not contribute to the natural resistance of L. monocytogenes to cephalosporins and monobactams, which is due to the low affinity of PBP3 and PBP5 for those antibiotics (24,34). Similarly, inactivation of lmo2229 had no effect on the sensitivity of the L. monocytogenes EGD/⌬lmo2229 mutant to nisin compared to the wild type; a slight increase in nisin sensitivity was previously reported in L. monocytogenes strain 412 upon lmo2229 disruption (12).…”

“…PBP3 was proposed to be the lethal target for ␤-lactams in L. monocytogenes (34), whereas increased expression of PBP4 together with a histidine kinase was associated with resistance to nisin (12,13), an antibacterial peptide which exerts its action by forming pores in the cytoplasmic membrane through interaction with the PG precursor lipid II (4). Although hundreds of proteins with GT-TP architecture have been identified, very few of them have been isolated and only a few of their properties have been characterized so far (3,8,28,30).…”

Listeria monocytogenesSurface Proteins: from Genome Predictions to Function

“…A first study reported that L. monocytogenes had five PBPs, as detected by their ability to bind benzylpenicillin (186). By searching the genome, Guinane and colleagues recently found seven surface proteins with similarities to PBPs (71).…”

“…PBPD1 (formerly VOL. 71,2007 LISTERIA SURFACE PROTEINS 387 PBP5 [186]) and PBPD2 are related to the peptidase S11 family (Pfam PF00768), represented by E. coli PBP5, while PBPD3 is related to the VanY DD-carboxypeptidase family (Pfam PF02557). L. monocytogenes clinical isolates are resistant to cephalosporins but are, fortunately, susceptible to penicillin and ampicillin, which constitute the major treatment for listeriosis in combination with the aminoglycoside gentamicin.…”

“…3A. The first family, including PBPA1 and PBPA2 (formerly PBP1 and PBP4 [186]), corresponds to class A PBPs, which are bifunctional proteins with an N-terminal transglycosylase domain and a C-terminal transpeptidase domain. The second family, including PBPB1, PBPB2, (formerly PBP2 [186]), and PBPB3, corresponds to class B PBPs, which have a C-terminal transpeptidase domain and an N-terminal PBP dimerization domain (Pfam PF03717) involved in interaction with other proteins during cell morphogenesis.…”