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The 2.4-A crystal structure of the penicillin-resistant penicillin-binding protein PBP5fm from Enterococcus faecium

E Sauvage1, F Kerff, E Fonzé

  • 1Centre d'Ingénierie des Protéines, Université de Liege, Institut de Physique, Belgium. eric.sauvage@ulg.ac.be

Cellular and Molecular Life Sciences : CMLS
|September 12, 2002
PubMed

Insights

The crystal structure of Enterococcus faecium PBP5fm reveals unique active site features, including a rigid loop and a sterically hindering residue, explaining its low affinity for beta-lactam antibiotics and natural resistance.

Area of Science:

  • Structural Biology
  • Microbiology
  • Biochemistry

Background:

  • Penicillin-binding proteins (PBPs) are crucial for bacterial cell wall synthesis and are primary targets for beta-lactam antibiotics.
  • Enterococci exhibit natural resistance to beta-lactams due to specific PBPs with low antibiotic affinity, such as PBP5fm in Enterococcus faecium.

Purpose of the Study:

  • To elucidate the structural basis of beta-lactam resistance in Enterococcus faecium by determining the crystal structure of PBP5fm.
  • To identify key structural features within the PBP5fm active site that contribute to its low affinity for beta-lactam antibiotics.

Main Methods:

  • X-ray crystallography was employed to determine the structure of the acyl-enzyme complex of PBP5fm with benzylpenicillin.
  • High-resolution (2.4 A) structural analysis was performed to examine the active site topology and key residues.

Main Results:

  • The crystal structure revealed a unique loop (residues 451-465) at the active site's edge, conferring rigidity via an Arg464-Asp481 salt bridge.
  • The Val465 residue within this loop points into the active site, reducing accessibility and likely accounting for PBP5fm's low affinity for beta-lactams.
  • This structural motif is conserved in other low-affinity PBPs, such as PBP2a and PBP3.

Conclusions:

  • The specific loop topology and the presence of Val465 are critical determinants of PBP5fm's low affinity for beta-lactams, explaining Enterococcus's natural resistance.
  • Understanding these structural features provides insights into antibiotic resistance mechanisms and potential targets for drug development.

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