Biopolym. Cell. 1985; 1(4):183-193.
Structure and Function of Biopolymers
Quantitative study of interaction of deacylated tRNA with the P, A and E sites of Escherichia coli ribosomes
1Semenkov Yu. P., 1Makarov E. M., 1Kirillov S. V.
  1. B. P. Konstantinov Institute of Nuclear Physics, Academy of Sciences of the USSR
    Gatchina, Leningrad distr., USSR
The association constants of deacylated tRNAPhe for the P site of 70S ribosomes were measured in the presence and absence of poly(U), and at different Mg2+ concentrations and temperatures. The numbers of Mg2+ ions involved in this interaction were determined: 4.4±0.3 (+poly(U) and 2.7±0.3 (–poly(U). The association constant of tRNAPhe for the A site was found to be 5·105M-1, much lower than that for the P site (2·109M–1), at 15 mM Mg2+, 200 mM NH4+ and 25 °C. The independence of the E-site binding of tRNAPhe on the messenger RNA was confirmed under these medium conditions. Based on the data obtained the affinity orders of aminoacyl-, peptidyl-tRNA and deacylated tRNA for the P, A and E sites are determined, and a possible mechanism of involvement of the E site in the translocation process is discussed.