Difference in the hydration water mobility around F-actin and myosin subfragment-1 studied by quasielastic neutron scattering.

Hydration water is essential for a protein to perform its biological function properly. In this study, the dynamics of hydration water around F-actin and myosin subfragment-1 (S1), which are the partner proteins playing a major role in various cellular functions related to cell motility including muscle contraction, was characterized by incoherent quasielastic neutron scattering (QENS). The QENS measurements on the DO- and HO-solution samples of F-actin and S1 provided the spectra of hydration water, from which the translational diffusion coefficient (D), the residence time (τ), and the rotational correlation time (τ) were evaluated. The D value of the hydration water of S1 was found to be much smaller than that of the hydration water of F-actin while the τ values were similar between S1 and F-actin. On the other hand, the τ values of the hydration water of S1 was found to be larger than that of the hydration water of F-actin. It was also found that the D and τ values of the hydration water of F-actin are similar to those of bulk water. These results suggest a significant difference in mobility of the hydration water between S1 and F-actin: S1 has the typical hydration water, the mobility of which is reduced compared with that of bulk water, while F-actin has the unique hydration water, the mobility of which is close to that of bulk water rather than the typical hydration water around proteins.