[Affinity modification of Escherichia coli ribosomes with the non-hydrolyzed GTP analog, gamma-[4-N-(2-chloroethyl)-N-methylaminobenzyl]amide of GTP].

Substituted gamma-amides of GTP viz. GTP gamma-[4-N-(2-chloro- and gamma-[4-N-(2-hydroxyethyl)-N-methylaminobenzyl]amide (CIRCH2NHpppG and OHRCH2NHpppG, resp.) were shown to be unhydrolisable GTP analogues in the EF-Tu-dependent GTP-ase reaction of ribosomes. The reactive analogue, CIRCH2NHpppG, was used for affinity labelling within the 70S ribosome.poly(U).tRNAPhe(P-site).Phe-tRNAPhe.EF-Tu.CIR[14C]CH2.NHpppG complex. Both 50S and 30S subunits were thus labelled but 50S subunit was modified considerably more than 30C subunit. Labelled were proteins L17, L21, S16, S21, and rRNA of both subunits, 23C rRNA within 50C subunit being labelled preferentially as compared with 50C proteins. No labelling of EF-Tu within the complex was detected.