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A GAP-GTPase-GDP-Pi Intermediate Crystal Structure Analyzed by DFT Shows GTP Hydrolysis Involves Serial Proton Transfers |
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| Authors: | Dr Robert W Molt Jr Dr Erika Pellegrini Dr Yi Jin |
| Institution: | 1. Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, 46202 USA
ENSCO, Inc., 4849 North Wickham Road, Melbourne, Florida, 32940 USA These authors contributed equally to the work.;2. 9 European Molecular Biology Laboratory, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble, Cedex 9, France These authors contributed equally to the work.;3. Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK |
| Abstract: | Cell signaling by small G proteins uses an ON to OFF signal based on conformational changes following the hydrolysis of GTP to GDP and release of dihydrogen phosphate (Pi). The catalytic mechanism of GTP hydrolysis by RhoA is strongly accelerated by a GAP protein and is now well defined, but timing of inorganic phosphate release and signal change remains unresolved. We have generated a quaternary complex for RhoA-GAP-GDP-Pi. Its 1.75 Å crystal structure shows geometry for ionic and hydrogen bond coordination of GDP and Pi in an intermediate state. It enables the selection of a QM core for DFT exploration of a 20 H-bonded network. This identifies serial locations of the two mobile protons from the original nucleophilic water molecule, showing how they move in three rational steps to form a stable quaternary complex. It also suggests how two additional proton transfer steps can facilitate Pi release. |
| Keywords: | computed proton states GTPase NMR spectroscopy phosphoryl transfer RhoA/RhoGAP |