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Ribosomal protein methylation in Escherichia coli: the gene prmA, encoding the ribosomal protein L11

A Vanet1, J A Plumbridge, M F Guérin

  • 1Institut de Biologie Physico-Chimique, URA1139 CNRS, Paris, France.

Molecular Microbiology
|December 1, 1994
PubMed

Insights

The Escherichia coli prmA gene encodes ribosomal protein L11-methyltransferase. Despite mutations causing undermethylation, a null mutation revealed the gene is not essential for viability, indicating residual enzyme activity.

Area of Science:

  • Molecular Biology
  • Microbiology
  • Enzymology

Background:

  • The prmA gene in Escherichia coli is responsible for the methyltransferase activity of ribosomal protein L11.
  • Mutations prmA1 and prmA3 lead to significantly undermethylated L11.
  • Previous understanding attributed no other effects to these mutations.

Purpose of the Study:

  • To investigate the function of the prmA gene and the impact of its mutations.
  • To characterize the PrmA protein and its enzymatic activity.
  • To determine the essentiality of prmA for Escherichia coli viability.

Main Methods:

  • DNA sequencing of mutant prmA alleles (prmA1, prmA3).
  • Construction of plasmids for overproducing wild-type and mutant PrmA proteins.
  • UV crosslinking assays to identify substrate binding.
  • In vitro methyltransferase assays using radiolabeled SAM.
  • Construction and chromosomal integration of a prmA null mutation via homologous recombination.

Main Results:

  • Point mutations were identified near the C-terminus in prmA1 and prmA3 alleles.
  • Wild-type PrmA protein crosslinked to S-adenosyl-L-methionine (SAM), confirming methyltransferase activity.
  • Mutant PrmA3 showed weak crosslinking to SAM.
  • Both mutant enzymes exhibited residual methyltransferase activity in vitro.
  • A strain with a null mutation in prmA was viable, indicating the gene is non-essential.

Conclusions:

  • The prmA gene encodes the ribosomal protein L11-methyltransferase.
  • Mutations prmA1 and prmA3 result in enzymes with residual activity, explaining the lack of a severe growth phenotype.
  • The prmA gene is not essential for Escherichia coli viability under tested conditions.

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