Effect of thiostrepton and 3′-terminal fragments of aminoacyl-tRNA on EF-Tu and ribosome-dependent GTP hydrolysis |
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Authors: | Prakash Bhuta Stanislav Chládek |
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Institution: | Michigan Cancer Foundation, 110 E. Warren Avenue, Detroit, MI 48201 U.S.A. |
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Abstract: | The effect of the antibiotics thiostrepton and micrococcin on EF-Tu-catalyzed (ribosome-dependent) GTP hydrolysis in the presence of A-Phe, C-A-Phe, or C-C-A-Phe (related to the sequence of the 3′-terminus of aminoacyl-tRNA)(System I) or by methanol (‘uncoupled GTPase’, System II) was investigated. In System I, thiostrepton increases the binding affinities of the effectors to the EF-Tu·GTP·70 S ribosome complex, as well as the extent of the GTP hydrolysis, while the KGTPm is virtually unchanged. Similarly, in the uncoupled system (System II) and in the absence of effectors, thiostrepton significantly increases VGTPmax, whereas KGTPm remains unaffected. Micrococcin is without any effect in both systems. The ‘uncoupled GTPase’ (in System II) is also strongly inhibited by C-A-Phe. The results indicate the crucial role of the EF-Tu site which binds the aminoacylated C-C-A terminus of aminoacyl-tRNA in promoting GTP hydrolysis. It follows that the binding of the model effectors (such as C-C-A-Phe) to that site is favorably influenced by the interaction of thiostrepton with the 50 S ribosomal subunit, whereas thiostrepton, per se, does not influence the affinity of EF-Tu for GTP. |
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Keywords: | Protein synthesis GTP hydrolysis Aminoacyl-tRNA fragment Thiostrepton Micrococcin (E coli) AA-tRNA aminoacyl transfer ribonucleic acid A-Phe TPCK To whom reprint requests should be addressed |
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