Chaperone properties of bacterial elongation factor EF-G and initiation factor IF2.
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.
Caldas
T
T
Biochimie Génétique, Institut Jacques Monod, Université Paris 7, 2 place Jussieu, 75005 Paris, France.
Laalami
S
S
Richarme
G
G
D002950:Citrate (si)-Synthase / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D018832:Molecular Chaperones / Q000378:metabolism*; D020653:Peptide Elongation Factor G / Q000378:metabolism*; D010448:Peptide Initiation Factors / Q000378:metabolism*; D039881:Prokaryotic Initiation Factor-2; D011489:Protein Denaturation; D017510:Protein Folding; D020673:Protein Renaturation; D013816:Thermodynamics; D014508:Urea; D000520:alpha-Glucosidases / Q000737:chemistry / Q000378:metabolism*
D018832:Molecular Chaperones; D020653:Peptide Elongation Factor G; D010448:Peptide Initiation Factors; D039881:Prokaryotic Initiation Factor-2; D014508:Urea; D002950:Citrate (si)-Synthase; D000520:alpha-Glucosidases; D020558:GTP Phosphohydrolases