Molecular dynamics study of time-correlated protein domain motions and molecular flexibility: cytochrome P450BM-3.

Time-correlated atomic motions were used to characterize protein domain boundaries from atomic coordinates generated by molecular dynamics simulations. A novel application of the dynamical cross-correlation matrix (DCCM) analysis tool was used to help identify putative protein domains. In implementing this new approach, several DCCM maps were calculated, each using a different coordinate reference frame from which protein domain boundaries and protein domain residue constituents could be identified. Cytochrome P450BM-3, from Bacillus megaterium, was used as the model protein in this study. The analyses indicated that the simulated protein comprises three distinct domain regions; in contrast, only two protein domains were identified in the original crystal structure report. Specifically, the DCCM analyses showed that the F-G helix region was a separate domain entity and not a part of the alpha domain, as previously designated. The simulations demonstrated that the domain motions of the F-G helix region effected both the size and shape of the enzyme active site, and that the dynamics of the F-G helix domain could possibly control access of substrate to the binding pocket.