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.
Highlights
The elongation phase of protein synthesis is promoted by two G proteins, elongation factor EF-Tu, 1 which delivers aminoacyl tRNAs to the ribosome, and EF-G, which catalyzes the translocation step, during which the A- and P-site tRNAs move to the P and E sites of the elongating ribosome, respectively, and mRNA is advanced by one codon [1,2,3]
We show that EF-G and initiation factor 2 (IF2), in a manner similar to that of molecular chaperones, increase the refolding of unfolded proteins, protect proteins against thermal denaturation, and form complexes with unfolded proteins
They were unfolded in the presence of 8 M urea, and allowed to refold upon dilution of the denaturant, in the absence or in the presence of EF-G
Summary
The elongation phase of protein synthesis is promoted by two G proteins, elongation factor EF-Tu, 1 which delivers aminoacyl tRNAs to the ribosome, and EF-G, which catalyzes the translocation step, during which the A- and P-site tRNAs move to the P and E sites of the elongating ribosome, respectively, and mRNA is advanced by one codon [1,2,3]. The stimulation of citrate synthase renaturation by EF-G in the absence of nucleotide or in the presence of GDP or GTP␥S was 2.6-, 2.4-, and 1.6-fold, respectively (Fig. 2A).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
