Intact aminoacyl-tRNA is required to trigger GTP hydrolysis by elongation factor Tu on the ribosome

GTP hydrolysis by elongation factor Tu (EF-Tu) on the ribosome is induced b y codon recognition. The mechanism by which a signal is transmitted from th e site of codon-anticodon interaction in the decoding center of the 30S rib osomal subunit to the site of EF-Tu binding on the 50S subunit is not known . Here we examine the role of the tRNA in this process. We have used two RN A fragments, one which contains the anticodon and D hairpin domains (ACD ol igomer) derived from tRNA(Phe) and the second which comprises the acceptor stem and T hairpin domains derived from tRNA(Ala) (AST oligomer) that amino acylates with alanine and forms a ternary complex with EF-Tu GTP. While the ACD oligomer and the ternary complex containing the Ala-AST oligomer inter act with the 30S and 50S A site, respectively, no rapid CTP hydrolysis was observed when both were bound simultaneously. The presence of paromomycin, an aminoglycoside antibiotic that binds to the decoding site and stabilizes codon-anticodon interaction in unfavorable coding situations, did not incr ease the rate of GTP hydrolysis. These results suggest that codon recogniti on as such is not sufficient for GTPase activation and that an intact tRNA molecule is required for transmitting the signal created by codon recogniti on to EE-Tu.