Chaperone properties of bacterial elongation factor EF-G and initiation factor IF2

J Biol Chem. 2000 Jan 14;275(2):855-60. doi: 10.1074/jbc.275.2.855.

Abstract

Elongation factor G(EF-G) and initiation factor 2 (IF2) are involved in the translocation of ribosomes on mRNA and in the binding of initiator tRNA to the 30 S ribosomal subunit, respectively. Here we report that the Escherichia coli EF-G and IF2 interact with unfolded and denatured proteins, as do molecular chaperones that are involved in protein folding and protein renaturation after stress. EF-G and IF2 promote the functional folding of citrate synthase and alpha-glucosidase after urea denaturation. They prevent the aggregation of citrate synthase under heat shock conditions, and they form stable complexes with unfolded proteins such as reduced carboxymethyl alpha-lactalbumin. Furthermore, the EF-G and IF2-dependent renaturations of citrate synthase are stimulated by GTP, and the GTPase activity of EF-G and IF2 is stimulated by the permanently unfolded protein, reduced carboxymethyl alpha-lactalbumin. The concentrations at which these chaperone-like functions occur are lower than the cellular concentrations of EF-G and IF2. These results suggest that EF-G and IF2, in addition to their role in translation, might be implicated in protein folding and protection from stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Citrate (si)-Synthase / chemistry
  • Citrate (si)-Synthase / metabolism*
  • Escherichia coli / metabolism*
  • GTP Phosphohydrolases / metabolism*
  • Hot Temperature
  • Kinetics
  • Molecular Chaperones / metabolism*
  • Peptide Elongation Factor G / metabolism*
  • Peptide Initiation Factors / metabolism*
  • Prokaryotic Initiation Factor-2
  • Protein Denaturation
  • Protein Folding*
  • Protein Renaturation
  • Thermodynamics
  • Urea
  • alpha-Glucosidases / chemistry
  • alpha-Glucosidases / metabolism*

Substances

  • Molecular Chaperones
  • Peptide Elongation Factor G
  • Peptide Initiation Factors
  • Prokaryotic Initiation Factor-2
  • Urea
  • Citrate (si)-Synthase
  • alpha-Glucosidases
  • GTP Phosphohydrolases