tRNA regions which contact with the ribosomal poly(U)-programmed P-site.

Equilibrium binding affinity of yeast tRNA(Phe) for Escherichia coli poly(U)-programmed 70S ribosomal P-site was compared with corresponding affinities of several tRNA(Phe) 3'- and 5'-end-truncated derivatives, all containing the anticodon arm. Our findings strongly suggest that besides three 3'-terminal-CCA nucleotides (C74, C75 and A76), only the tRNA(Phe) anticodon arm (N28-N42) contains ribosomal P-site contact centers and that there are no such centers in the intermediate regions N1-N27 and N43-N73.

On the binding of isolated yeast tRNA(Phe) anticodon arm to Escherichia coli 30S and 70S ribosomes. Guanosine-42 is important for the binding.

Conditions for the reversible binding of isolated anticodon arm of yeast tRNA(Phe) (15-nucleotide, corresponding to nucleotides N28-N42) to the P site of Escherichia coli 30S and 70S ribosomes have been determined. The affinity constant for the anticodon arm binding to 70S ribosomes is shown to be only 30-fold weaker than that for the binding of total tRNA(Phe). The affinities of yeast tRNA(Phe) and the anticodon arm for 30S subunits and of the anticodon arm for the total 70S ribosomes are shown to be equal.

70-S ribosomes of Escherichia coli have an additional site for deacylated tRNA binding.

Escherichia coli 70-S ribosomes contain a third site for tRNA binding, additional to the A and P sites. This conclusion is based on several findings. Direct measurements showed that in the presence of poly(U), when both A and P sites are occupied by Ac[14C]Phe-tRNAPhe, ribosomes are capable of binding additionally deacylated non-cognate [3H]tRNA.

On the mechanism of interaction of N-acetylphenylalanyl-tRNAPhe with ribosomes of Escherichia coli: effect of antibiotics and Tp psi pCpGp.

The tetranucleotide Tp psi pCpGp acts as a specific inhibitor of the rate of AcPhe-tRNAPhe binding in the ribosomal P site. This effect is observed both in the presence and in the absence of poly(U). In the absence of poly(U) antibiotics tetracycline and puromycin also decrease the rate of AcPhe-tRNAPhe binding.

Quantitative study of the interaction of formylmethionyl-tRNAfMet with ribosomes of Escherichia coli.

fMet-tRNAfMet binds reversibly to the donor site (P-site) of Escherichia coli ribosomes both in the absence of messenger and in the presence of ApUpGp and some other oligonucleotides or poly(U). Kinetics of interaction conforms the second-order law. The equilibrium constants and the rate constants of binding are estimated at 0 degrees C.