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A GAP‐GTPase‐GDP‐P i Intermediate Crystal Structure Analyzed by DFT Shows GTP Hydrolysis Involves Serial Proton Transfers
Author(s) -
Molt Robert W.,
Pellegrini Erika,
Jin Yi
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201901627
Subject(s) - gtpase , gtp' , rhoa , chemistry , proton , crystallography , hydrogen bond , small gtpase , molecule , stereochemistry , signal transduction , enzyme , biochemistry , organic chemistry , physics , quantum mechanics
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 (P i ). 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‐P i . Its 1.75 Å crystal structure shows geometry for ionic and hydrogen bond coordination of GDP and P i 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 P i release.