Penicillin-binding Protein 2x of Streptococcus pneumoniae: Three New Mutational Pathways for Remodelling an Essential Enzyme into a Resistance Determinant

• Published in: Journal of molecular biology 2008-03, Vol.376 (5), p.1403-1416
• Main Authors: Maurer, Patrick, Koch, Barbara, Zerfaß, Ilka, Krauß, Jan, van der Linden, Mark, Frère, Jean-Marie, Contreras-Martel, Carlos, Hakenbeck, Regine
• Format: Article
• Language: English
• Subjects: beta-Lactam Resistance; cefotaxime; Cefotaxime - pharmacology; Humans; Models, Molecular; PBP2x; penicillin resistance; penicillin-binding protein; Penicillin-Binding Proteins - chemistry; Penicillin-Binding Proteins - genetics; Penicillin-Binding Proteins - metabolism; Peptidyl Transferases - genetics; Peptidyl Transferases - metabolism; Pneumococcal Infections - microbiology; Point Mutation; Protein Structure, Secondary; Protein Structure, Tertiary; Streptococcus pneumoniae; Streptococcus pneumoniae - chemistry; Streptococcus pneumoniae - drug effects
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2007.12.058

Mutations in the transpeptidase domain of penicillin-binding protein 2x (PBP2x) of Streptococcus pneumoniae that reduce the affinity to beta-lactams are important determinants of resistance to these antibiotics. We have now analyzed in vitro and in vivo properties of PBP2x variants from cefotaxime-resistant laboratory mutants and a clinical isolate. The patterns of two to four resistance-specific mutations present in each of the proteins, all of which are placed between 6.6 and 24 Å around the active site, fall into three categories according to their positions in the three-dimensional structure. The first PBP2x group is characterized by mutations at the end of helix α11 and carries the well-known T550A change and/or one mutation on the surface of the penicillin-binding domain in close contact with the C-terminal domain. All group I proteins display very low acylation efficiencies, ≤ 1700 M − 1 s − 1 , for cefotaxime. The second class represented by PBP2x of the mutant C505 shows acylation efficiencies below 100 M − 1 s − 1 for both cefotaxime and benzylpenicillin and contains the mutation L403F at a critical site close to the active serine. PBP2x of the clinical isolate 669 reveals a third mutational pathway where at least the two mutations Q552E and S389L are important for resistance, and acylation efficiency is reduced for both beta-lactams to around 10,000 M − 1 s − 1 . In each group, at least one mutation is located in close vicinity to the active site and mediates a resistance phenotype in vivo alone, whereas other mutations might exhibit secondary effects only in context with other alterations.