In the presence of Escherichia coli ribosomes and elongation factor EF) Tu, 2'(3')-O-L-phenylalanyladenosine (AdoPhe), the 3'-terminal portion of Phe-tRNAPhe, promotes the hydrolysis of GTP. The reaction requires the presence of both 30S and 50S ribosomal subunits and of proteins L7/L12 on the 50S subunit, is unaffected by mRNA [poly(uridylic acid)], and is strongly stimulated by EF-Ts. It is proposed that the AdoPhe-dependent GTP hydrolysis, like that promoted by aminoacyl-tRNA, is mediated by a ternary complex with EF-Tu and GTP; however, in contrast to aminoacyl-tRNA, AdoPhe is probably not retained by ribosomes after GTP hydrolysis. Phe-tRNAPhe or N-acetyl-Phe-tRNAPhe bound to the ribosomal acceptor site do not inhibit, but even stimulate, GTP hydrolysis by AdoPhe.EF-Tu.GTP. Thus, the binding site for EF-Tu on the ribosome is probably available for interaction with AdoPhe.EF-Tu.GTP regardless of whether the nearby acceptor site is vacant of occupied with aminoacyl-tRNA or peptidyl-tRNA. The results demonstrate the critical role of the 3'-terminal region of aminoacyl-tRNA in activating the EF-Tu- plus ribosome-dependent GTPase.
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| http://dx.doi.org/10.1073/pnas.77.2.905 | DOI Listing |
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