Matsuo Tatsuhito, Arata Toshiaki, Oda Toshiro, Nakajima Kenji, Ohira-Kawamura Seiko, Kikuchi Tatsuya, Fujiwara Satoru
Quantum Beam Science Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan.
Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Biochem Biophys Rep. 2016 Apr 30;6:220-225. doi: 10.1016/j.bbrep.2016.04.013. eCollection 2016 Jul.
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.
水合水对于蛋白质正常发挥其生物学功能至关重要。在本研究中，通过非相干准弹性中子散射（QENS）对F-肌动蛋白和肌球蛋白亚片段-1（S1）周围的水合水动力学进行了表征，F-肌动蛋白和S1是在包括肌肉收缩在内的与细胞运动相关的各种细胞功能中起主要作用的伴侣蛋白。对F-肌动蛋白和S1的DO溶液和HO溶液样品进行的QENS测量提供了水合水的光谱，据此评估了平移扩散系数（D）、停留时间（τ）和旋转相关时间（τ）。发现S1水合水的D值远小于F-肌动蛋白水合水的D值，而S1和F-肌动蛋白的τ值相似。另一方面，发现S1水合水的τ值大于F-肌动蛋白水合水的τ值。还发现F-肌动蛋白水合水的D值和τ值与体相水的相似。这些结果表明S1和F-肌动蛋白的水合水流动性存在显著差异：S1具有典型的水合水，其流动性相对于体相水降低，而F-肌动蛋白具有独特的水合水，其流动性接近体相水而非蛋白质周围典型的水合水。
