Computational Modeling of the Neurofibromin-Stimulated Guanosine Triphosphate Hydrolysis by the KRas Protein

We report the results of computational studies of the guanosine triphosphate (GTP) hydrolysis in the active site of the KRas-NF1 protein complex, where KRas stands for the K-isoform of the Ras (ras sarcoma) protein and NF1 (neurofbromin-1) is the activating protein. The model system was constructed using coordinates of heavy atoms from the crystal structure PDB ID 6OB2 with the GTP analog GMPPNP. Large-scale classical molecular dynamics (MD) calculations were performed to analyze conformations of the enzyme-substrate complexes. The Gibbs energy profiles for the hydrolysis reaction were computed using MD simulations with quantum mechanics/molecular mechanics (QM/MM) interaction potentials. The density functional theory DFT(ωB97X-D3/6-31G**) approach was applied in QM and the CHARMM36 force field parameters in MM. The most likely scenario of the chemical step of the GTP hydrolysis in KRas-NF1 corresponds to the water-assisted mechanism of the formation of the inorganic phosphate coupled with the dissociation of GTP to GDP.