2'(3')-O-Glycyl oligoribonucleotides with sequences of the 3'-terminus of glycyl-tRNA: chemical synthesis and properties in partial reactions of protein biosynthesis

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Abstract
Specific syntheses of 2''(3'')-O-aminoacyl oligoribonucleotides C-C-A-Gly (12), C-C-A(AcGly) (7), U-C-C-A-Gly (17), and C-U-C-C-A-Gly (19), which are the 3''-terminal sequences of Escherichia coli Gly-tRNA (or AcGly-tRNA, respectively) are described. Compounds 12, 17, and 19 were synthesized by employing the benzotriazolyl phosphotriester approach with the following protection groups on the components: benzoyl for the heterocyclic amino groups, 2-chlorophenyl group for internucleotide phosphate protection, dimethoxytrityl and levulinoyl groups for blocking of the 5''-hydroxyl, methoxytetrahydropyranyl group for protection of the 2''-hydroxyl functions, and N-(benzyloxycarbonyl)orthoglycinate as the masked aminoacyl group simultaneously protecting the 2'',3''-cis diol group of the 3''-terminal adenosine moiety. The fully protected tri-, tetra-, and pentanucleotides were obtained via 5''-extension of di- and trinucleotide blocks after prior selective removal of the 5''-O-levulinoyl group with hydrazine. The blocked derivatives 11, 16, and 18 were totally deprotected by reactions with NH4OH, H+ and H2/Pd to yield the target compounds 12, 17, and 19 in good yields. C-C-A(AcGly) (7) was synthesized according to a stepwise procedure via activation of preformed diesters with (mesitylenesulfonyl)tetrazole. C-C-A-Gly (12), U-C-C-A-Gly (17), and C-U-C-C-A-Gly (19) were all acceptor substrates in the peptidyltransferase reaction with the Ac-Phe-tRNA-70S ribosome-poly(U) system. All three models also promoted EF-Tu-70S ribosome GTP hydrolysis. Since activities of compounds 12, 17, and 19 in both systems are quite similar, addition of nucleotides next to the common C-C-A sequence of tRNA does not appear to enhance binding of these models to either peptidyltransferase A site or EF-Tu. The GTPase-promoting activity of C-C-A-Gly (12) in the EF-Tu-70S ribosome system is greatly stimulated by presence of EF-Ts. C-C-A(AcGly) (7) was completely inactive as a donor in the peptidyltransferase reaction with Phe-tRNA in the 70S ribosome system under fragment reaction conditions.

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