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Cell wall branches, penicillin resistance and the secrets of the MurM protein

András Fiser1, Sergio R Filipe, Alexander Tomasz

  • 1Department of Biochemistry and Seaver Foundation Center for Bioinformatics, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461, USA.

Trends in Microbiology
|December 9, 2003
PubMed

Insights

Penicillin resistance in pneumococci requires more than altered penicillin-binding proteins (PBPs). The novel protein MurM is crucial for cell wall synthesis and penicillin resistance, as its inactivation eliminates both.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Structural Biology

Background:

  • Penicillin resistance in Streptococcus pneumoniae is complex.
  • Altered penicillin-binding proteins (PBPs) are necessary but not sufficient for resistance.
  • The role of other proteins in cell wall synthesis and resistance was unclear.

Purpose of the Study:

  • To investigate the role of the newly identified protein MurM in pneumococcal penicillin resistance.
  • To understand the function of MurM and MurN in pneumococcal cell wall synthesis.
  • To elucidate the structural basis of MurM's function through 3D modeling.

Main Methods:

  • Genetic inactivation of the murM gene in Streptococcus pneumoniae.
  • Analysis of cell wall structure in murM-deficient mutants.
  • Construction of a 3D model of the MurM protein.

Main Results:

  • Inactivation of murM resulted in cell walls lacking peptide branches.
  • MurM-deficient cells completely lost penicillin resistance.
  • The 3D model of MurM provided structural context for biochemical and genetic data.

Conclusions:

  • MurM, along with MurN, is essential for synthesizing peptide branches in the pneumococcal cell wall.
  • MurM is a critical factor for achieving penicillin resistance in pneumococci.
  • Structural insights into MurM aid in understanding its role in cell wall biosynthesis and resistance mechanisms.

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