(19)F?NMR and DFT Analysis Reveal Structural and Electronic Transition State Features for RhoA-Catalyzed GTP Hydrolysis.

ABSTRACT: Molecular details for RhoA/GAP catalysis of the hydrolysis of GTP to GDP are poorly understood. We use (19)F?NMR chemical shifts in the MgF3(-) transition state analogue (TSA) complex as a spectroscopic reporter to indicate electron distribution for the ?-PO3(-) oxygens in the corresponding TS, implying that oxygen coordinated to Mg has the greatest electron density. This was validated by QM calculations giving a picture of the electronic properties of the transition state (TS) for nucleophilic attack of water on the ?-PO3(-) group based on the structure of a RhoA/GAP-GDP-MgF3(-) TSA complex. The TS model displays a network of 20 hydrogen bonds, including the GAP Arg85' side chain, but neither phosphate torsional strain nor general base catalysis is evident. The nucleophilic water occupies a reactive location different from that in multiple ground state complexes, arising from reorientation of the Gln-63 carboxamide by Arg85' to preclude direct hydrogen bonding from water to the target ?-PO3(-) group.

SUBMITTER: Jin Y 

PROVIDER: S-EPMC4770445 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature