Stabilization of G Domain Conformations in the tRNA-modifying MnmE-GidA Complex Observed with Double Electron Electron Resonance Spectroscopy |
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Authors: | Sabine B?hme Simon Meyer André Krüger Heinz-Jürgen Steinhoff Alfred Wittinghofer Johann P Klare |
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Institution: | From the ‡Department of Physics, University of Osnabrück, Barbarastrasse 7, D-49076 Osnabrück, Germany and ;the §Department of Structural Biology, Max-Planck-Institute of Molecular Physiology, Otto Hahn Strasse 11, D-44227 Dortmund, Germany |
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Abstract: | MnmE is a GTP-binding protein conserved between bacteria and eukarya. It is a dimeric three-domain protein where the two G domains have to approach each other for activation of the potassium-stimulated GTPase reaction. Together with GidA, in a heterotetrameric α2β2 complex, it is involved in the modification of the wobble uridine base U34 of the first anticodon position of particular tRNAs. Here we show, using various spin-labeled MnmE mutants and EPR spectroscopy, that GidA binding induces large conformational and dynamic changes in MnmE. It stimulates the GTPase reaction by stabilizing the GTP-bound conformation in a potassium-independent manner. Surprisingly, GidA binding influences not only the GTP- but also the GDP-bound conformation. Thus GidA is a new type of regulator for a G protein activated by dimerization. |
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Keywords: | Biophysics Electron Paramagnetic Resonance (EPR) G Proteins Protein-Protein Interactions Transfer RNA (tRNA) G Protein Activated by Dimerization GidA MnmE tRNA Modification |
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