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The pretranslocation ribosome is targeted by GTP-bound EF-G in partially activated form.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Biology. (ehrenberg)
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia.
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia.
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia.
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2008 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 105, no 41, 15678-83 p.Article in journal (Refereed) Published
Abstract [en]

Translocation of the tRNA x mRNA complex through the bacterial ribosome is driven by the multidomain guanosine triphosphatase elongation factor G (EF-G). We have used isothermal titration calorimetry to characterize the binding of GDP and GTP to free EF-G at 4 degrees C, 20 degrees C, and 37 degrees C. The binding affinity of EF-G is higher to GDP than to GTP at 4 degrees C, but lower at 37 degrees C. The binding enthalpy and entropy change little with temperature in the case of GDP binding but change greatly in the case of GTP binding. These observations are compatible with a large decrease in the solvent-accessible hydrophobic surface area of EF-G on GTP, but not GDP, binding. The explanation we propose is the locking of the switch 1 and switch 2 peptide loops in the G domain of EF-G to the gamma-phosphate of GTP. From these data, in conjunction with previously reported structural data on guanine nucleotide-bound EF-G, we suggest that EF-G enters the pretranslocation ribosome as an "activity chimera," with the G domain activated by the presence of GTP but the overall factor conformation in the inactive form typical of a GDP-bound multidomain guanosine triphosphatase. We propose that the active overall conformation of EF-G is attained only in complex with the ribosome in its "ratcheted state," with hybrid tRNA binding sites.

Place, publisher, year, edition, pages
2008. Vol. 105, no 41, 15678-83 p.
Keyword [en]
GTPase, guanine nucleotide binding, isothermal titration calorimetry, thermodynamic parameters of interaction
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
Identifiers
URN: urn:nbn:se:uu:diva-104039DOI: 10.1073/pnas.0807912105ISI: 000260240900010PubMedID: 18836081OAI: oai:DiVA.org:uu-104039DiVA: diva2:219276
Available from: 2009-05-27 Created: 2009-05-27 Last updated: 2017-12-13Bibliographically approved

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