title: Equilibrium measurements of cognate and noncognate interactions between aminoacyl transfer RNA synthetases and transfer RNA.
abstract: The interaction of Escherichia coli isoleucyl-tRNA synthetase with its cognate and five noncognate tRNAs, and of yeast valyl-tRNA synthetase with its cognate and four noncognate tRNAs, has been measured directly by fluorescence quenching. The cognate associations are strongest (association constant of 10(8) M-1 or more at pH 5.5, 17 degrees). A wide variation is found in the strengths of the noncognate interactions; these have association constants smaller than that of these cognate association by a factor of less than 10 to over 10(4), depending on the enzyme-t-RNA pair. A more detailed study of the cognate isoleucyl-tRNA synthetase-tRNAIle association suggests that the strength of the interaction is markedly sensitive to a pH-dependent transition in the enzyme centered at pH 6 on the other hand, Mg2+-induced structural changes in tRNAIle at 17 degrees in low salt do not greatly affect the availability of the nucleic acid's receptor sites for enzyme...
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D001665:Binding Sites; D004926:Escherichia coli / Q000201:enzymology; D005973:Glutamine; D006863:Hydrogen-Ion Concentration; D007533:Isoleucine-tRNA Ligase / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008433:Mathematics; D010649:Phenylalanine; D011485:Protein Binding; D012329:RNA, Bacterial; D012343:RNA, Transfer; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013045:Species Specificity; D013050:Spectrometry, Fluorescence; D014637:Valine-tRNA Ligase / Q000378:metabolism*
chemical_list: D012329:RNA, Bacterial; D005973:Glutamine; D010649:Phenylalanine; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases; D007533:Isoleucine-tRNA Ligase; D014637:Valine-tRNA Ligase; D008274:Magnesium