Equivalent and Non‐equivalent Binding Sites for tRNA on Aminoacyl‐tRNA Synthetases

Abstract

Complexes between tRNA^Phe (yeast), tRNA^Ser (yeast) and tRNA^Tyr (Escherichia coli) and their cognate aminoacyl‐tRNA synthetases have been studied by sedimentation velocity runs in an analytical ultracentrifuge. The amount of complex formation was determined by the absorption and the sedimentation coefficients of the fast‐moving boundary in the presence of excess tRNA or excess synthetase respectively. The same method has been applied to unspecific combinations of tRNAs and synthetases. Inactive material of tRNA or synthetase does not influence the results. The binding data are discussed with respect to the tertiary structure of the tRNAs, the subunit structure of the synthetases and the possible physical basis for the non‐equivalence of binding sites.