RELATIVE AFFINITIES OF ALL ESCHERICHIA-COLI AMINOACYL-TRANSFER RNAS FOR ELONGATION-FACTOR TU-GTP

  • 1 January 1984
    • journal article
    • research article
    • Vol. 259  (8) , 5010-5016
Abstract
The relative affinities of all E. coli aminoacyl-tRNA for E. coli elongation factor (EF) Tu-GTP were measured by 2 independent applications of the competition form of the RNase resistance assay. The set of aminoacyl-tRNA includes at least 1 tRNA for each of the 20 amino acids and purified isoacceptor tRNA species for arginine, glycine, leucine, lysine and tyrosine. In the 1st competition study, [3H]Phe-tRNA was used as the competing aminoacyl-tRNA against [14C]aminoacyl-tRNA in the set of all tRNA; in the 2nd study, [3H]Leu-tRNA4Leu was used as the competing aminoacyl-tRNA. The relative order of aminoacyl-tRNA affinities for EF-Tu-GTP was the same in each study. Apparently, the affinity of EF-Tu-GTP at 4.degree. C, pH 7.4, is strongest for Gln-tRNA and weakest for Val-tRNA. Both Gly-tRNA and Pro-tRNA bind very strongly to EF-Tu-GTP relative to other aminoacyl-tRNA. Various models of ternary complex interactions are discussed in light of the new data. Although the properties of the amino acid substitutent are primarily responsible for the differences in relative affinities among the noninitiator aminoacyl-tRNA, the results for the 4 isoacceptor species of Leu-tRNALeu indicate that the secondary structural features of the tRNA are also influential.