THE ELONGATION-FACTOR TU BINDS AMINOACYL-TRANSFER RNA IN THE PRESENCE OF GDP

  • 1 January 1982
    • journal article
    • research article
    • Vol. 257  (19) , 1261-1267
Abstract
Escherichia coli elongation factor (EF-Tu) binds aminoacyl-tRNA (aa-tRNA) in the presence of GTP and in the presence of GDP. Complex formation leads to a protection of the aa-tRNA against nonenzymatic deacylation and digestion by pancreatic RNase, and to a protection of EF-Tu against proteolysis by trypsin. The equilibrium constant for the binding of yeast Phe-tRNAPhe to EF-Tu.cntdot.GDP is 0.7 .times. 105 M-1, which is 2 orders of magnitude lower than the equilibrium constant for yeast Phe-tRNAPhe binding to EF-Tu.cntdot.GTP. In the presence of kirromycin, aa-tRNA binding to EF-Tu.cntdot.GDP is not affected as much: yeast Phe-tRNAPhe is bound with an equilibrium constant of 3 .times. 105 M-1. While there is also a measurable interaction between EF-Tu.cntdot.GTP and tRNA, such an interaction cannot be detected with EF-Tu.cntdot.GDP and tRNA, not even at millimolar concentrations. A so far undetected complex formation between aa-tRNA and EF-Tu.cntdot.GTP in the presence of pulvomycin, however, could be detected. The results are discussed in terms of the structural requirements of ternary complex formation and in the light of proofreading schemes involving A-site binding on the E. coli ribosome.

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