[Study of the poly(U)-dependent interaction of tRNA(Phe) with the P-site of Escherichia coli ribosomes by chemical modification with nitrosoethylurea].

The accessibility of phosphates in E. coli tRNA(Phe) bound to E. coli ribosomes and 30S subunits for attack by an alkylating agent ethylnitrosourea was studied.

[Binding of a fragment of yeast phenylalanyl tRNA containing an anticodon loop with 30S and 70S ribosomes from Escherichia coli. The role of guanosine-42 in this interaction].

Poly(U)-dependent binding of isolated yeast tRNA(Phe) anticodon hairpin (15-nucleotide-long, corresponding to nucleotides 28-42 within the tRNA) and several its derivatives to the P site of Escherichia coli 30S and 70S ribosomes was studied quantitatively. The affinity for the hairpin binding to 70S ribosomes was shown to be only 30-fold weaker than that for the binding of total tRNA(Phe). Within the anticodon hairpin, removal of the 3'-terminal nucleotide corresponding to guanosine-42 in tRNA(Phe) decreases the association constant for the anticodon arm-ribosome interaction 15-fold.

[Selectivity of A-site on Escherichia coli ribosomes in relation to deacylation of transfer RNA].

To evaluate the equilibrium affinity of several deacylated tRNA from E. coli and yeast tRNA(Phe) for the A site of poly(U)- and poly(A)-programmed E. coli ribosomes, we studied their inhibitory effect on the subsequent binding of the template-cognate ternary complex EFTu*GTP* [14C]aminoacyl-tRNA.

[Poly(U)-dependent interaction of yeast tRNA(Phe) and its fragments with Escherichia coli ribosomes. II. Localization of tRNA binding centers with a P-site].

Poli(U)-dependent binding of yeast tRNA(Phe) lacking the 3'-terminal CA or CCA residues, and fragments of tRNA prepared by splitting the tRNA(Phe) at the G18 or 7mG46 nucleotides, to the 70S ribosomal P-site was studied. Equilibrium binding constants and free energies of binding were measured. The contribution of C74 and C75 was estimated at 3.

[Poly(U)-dependent interaction of yeast tRNA(Phe) and its fragments with ribosomes from Escherichia coli].

The poly(U)-dependent bindings of yeast tRNAPhe, its derivative depleted of 3'-terminal adenosine, and 15-nucleotide having a sequence of yeast tRNAPhe anticodon arm to the P site of Escherichia coli 70S ribosomes were compared. The equilibrium and rate constants were determined. Data indicate that the anticodon arm (N28-N42) contributes the major fraction of the binding free energy (-45.