The elongation factor Tu from Escherichia coli, aminoacyl-tRNA, and guanosine tetraphosphate form a ternary complex which is bound by programmed ribosomes.

Abstract

The interaction of the Escherichia coli elongation factor Tu guanosine tetraphosphate complex (EF-Tu ppGpp) with aminoacyl-tRNAs(aa-tRNA) was reinvestigated by gel filtration and hydrolysis protection experiments. These experiments show that EF-Tu X ppGpp like EF-Tu X GDP (Pingoud, A., Block, W., Wittinghofer, A., Wolf, H. & Fischer, E. (1982) J. Biol. Chem. 257, 11261-11267) forms a fairly stable complex with Phe-tRNAPhe, KAss being 0.6 X 10(5) M-1 at 25 degrees C. The binding of the EF-Tu X ppGpp X aa-tRNA complex to programmed ribosomes was investigated by a centrifugation technique. It is shown that this complex is bound codon-specific with KAss = 3 X 10(7) M-1 at 0 degrees C and that it stimulates peptidyl transfer. A numerical estimation of the intracellular concentration of EF-Tu X GTP X aa-tRNA and EF-Tu X ppGpp X aa-tRNA during normal growth and under the stringent response indicates that ppGpp accumulation does affect the EF-Tu X GTP X aa-tRNA concentration but does not lead to major depletion of this pool. Furthermore, due to the higher affinity of EF-Tu X GTP to aa-tRNA and of the ternary complex EF-Tu X GTP X aa-tRNA to the ribosome, EF-Tu X ppGpp X aa-tRNA binding to the ribosome is not significant. According to our measurements and calculations, therefore, a direct participation of EF-Tu in slowing down the rate of protein biosynthesis and improving its accuracy during amino acid starvation is not obvious.

• Authors: A Pingoud, F U Gast, W Block, F Peters
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 258 Issue 23 Pg. 14200-5 (Dec 10 1983) ISSN: 0021-9258 [Print] United States
• PMID: 6358217 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Macromolecular Substances
• Peptide Elongation Factors
• RNA, Transfer, Amino Acyl
• Guanosine Tetraphosphate
• Guanosine Triphosphate
• Peptide Elongation Factor Tu

Topics

• Escherichia coli
• Guanosine Tetraphosphate (metabolism)
• Guanosine Triphosphate (metabolism)
• Macromolecular Substances
• Peptide Elongation Factor Tu
• Peptide Elongation Factors (metabolism)
• RNA, Transfer, Amino Acyl (metabolism)
• Ribosomes (metabolism)