[Stoichiometry of GTP hydrolysis during peptide synthesis on the ribosome. GTP hydrolysis uncoupled with ribosomal peptide synthesis and dependent on preparation of elongation factor T].

It is shown that preparations of EF-T are practically free from GTPase activity, if they were formed from EF-Tu and EF-Ts carefully purified from GTPase beforehand. Some Ef-T-dependent GTPase can arise after addition of tRNA or aminoacyl-tRNA preparations to a EF-T+ribosomes mixture. Poly(U) stimulates, as a rule, EF-T-dependent GTPase in the EF-T/ribosomes+tRNA mixture. Uncoupled EF-T-dependent GTPase of the EF-T+ribosomes+tRNA+poly(U) mixture is by 1--2 orders of magnitude less than uncoupled EF-G-dependent GTPase under the same conditions. A conclusion is made that uncoupled EF-T-dependent GTPase is an inevitable obstacle when studying the GTP expenditure in the process of ribosomal protein synthesis, if a traditional cell-free protein-synthesizing system is used for this purpose.