Role of a ribosomal RNA phosphate oxygen during the EF-G-triggered GTP hydrolysis.

Date publication

mai 2015

Journal

Proceedings of the National Academy of Sciences of the United States of America

Auteurs

Membres identifiés du Cancéropôle Est :
Dr ENNIFAR Eric

Tous les auteurs :
Koch M, Flür S, Kreutz C, Ennifar E, Micura R, Polacek N

Lien Pubmed

https://www.ncbi.nlm.nih.gov/pubmed/25941362

Résumé

Elongation factor-catalyzed GTP hydrolysis is a key reaction during the ribosomal elongation cycle. Recent crystal structures of G proteins, such as elongation factor G (EF-G) bound to the ribosome, as well as many biochemical studies, provide evidence that the direct interaction of translational GTPases (trGTPases) with the sarcin-ricin loop (SRL) of ribosomal RNA (rRNA) is pivotal for hydrolysis. However, the precise mechanism remains elusive and is intensively debated. Based on the close proximity of the phosphate oxygen of A2662 of the SRL to the supposedly catalytic histidine of EF-G (His87), we probed this interaction by an atomic mutagenesis approach. We individually replaced either of the two nonbridging phosphate oxygens at A2662 with a methyl group by the introduction of a methylphosphonate instead of the natural phosphate in fully functional, reconstituted bacterial ribosomes. Our major finding was that only one of the two resulting diastereomers, the SP methylphosphonate, was compatible with efficient GTPase activation on EF-G. The same trend was observed for a second trGTPase, namely EF4 (LepA). In addition, we provide evidence that the negative charge of the A2662 phosphate group must be retained for uncompromised activity in GTP hydrolysis. In summary, our data strongly corroborate that the nonbridging proSP phosphate oxygen at the A2662 of the SRL is critically involved in the activation of GTP hydrolysis. A mechanistic scenario is supported in which positioning of the catalytically active, protonated His87 through electrostatic interactions with the A2662 phosphate group and H-bond networks are key features of ribosome-triggered activation of trGTPases.

Mots clés

Catalysis, GTP Phosphohydrolases, metabolism, Guanosine Triphosphate, metabolism, Histidine, metabolism, Hydrolysis, Models, Biological, Mutagenesis, Organophosphorus Compounds, metabolism, Oxygen, metabolism, Peptide Elongation Factor G, metabolism, Peptide Elongation Factor Tu, metabolism, Phosphates, analysis, Protein Biosynthesis, physiology, RNA, Ribosomal, metabolism

Référence

Proc. Natl. Acad. Sci. U.S.A.. 2015 May 19;112(20):E2561-8