Biopolymers and cell. 1988. Volume 4. № 1. 3 - 7

A. A. Gobslitis, V. B. Odinzov, S. V. Kirillov

THERMODYNAMICS OF INTERACTION OF DEACYLATED INITIATOR tRNA AND AMINOACYL-tRNA WITH P- AND A-SITES OF 30S SUBUNITS OF ESCHERICHIA COLI RIBOSOMES PROGRAMMED BY AUG(U)n

Summary

    Small ribosomal subunit of E. coli ribosome programmed by AUG(U)n is capable to bind two molecules of tRNA (tRNA,Met or fMet-tRNAiMet plus Phe-tRNAphe). tRNAfMet is. bound to P-site of SOS subunit of the complex [30S+AUG(U),,] (or to the site overlapped with P-site). Phe-tRNAphe is bound to A-site of 30S subunits of the complex [30S + 4-AUG(U)n+tRNAfMet] and its binding is inhibited by tetracycline. The association constants tRNAfMet with the complex [30S+AUG(U)n] and Phe-tRNAphe with the complex [30S+AUG(U)n+tRNAfMet] are measured at different temperatures and magnesium concentrations and thermodynamic parameters of these interactions are calculated. When fMet-tRNA[Met is bound instead of tRNAtMet, dipeptide (fMet-Phe) formation is observed after addition of SOS subunits. Thus, there are two tRNA binding sites on 30 S subunits which are realized as functional P- and A-sites of 70S ribosome not only in the poly(U)-dependent system but in the studied system with matrix carrying an initiator :odon AUG.