Department of Materials Processing, Graduate School of Tohoku University, 6-6-02 Aobayama, Aoba-Ku, Sendai, Miyagi 980-8579, Japan.
Biochem Biophys Res Commun. 2011 Jan 28;404(4):985-90. doi: 10.1016/j.bbrc.2010.12.096. Epub 2010 Dec 25.
This paper reports that water molecules around F-actin, a polymerized form of actin, are more mobile than those around G-actin or in bulk water. A measurement using pulse-field gradient spin-echo (1)H NMR showed that the self-diffusion coefficient of water in aqueous F-actin solution increased with actin concentration by ∼5%, whereas that in G-actin solution was close to that of pure water. This indicates that an F-actin/water interaction is responsible for the high self-diffusion of water. The local viscosity around actin was also investigated by fluorescence measurements of Cy3, a fluorescent dye, conjugated to Cys 374 of actin. The steady-state fluorescence anisotropy of Cy3 attached to F-actin was 0.270, which was lower than that for G-actin, 0.334. Taking into account the fluorescence lifetimes of the Cy3 bound to actin, their rotational correlation times were estimated to be 3.8 and 9.1ns for F- and G-actin, respectively. This indicates that Cy3 bound to F-actin rotates more freely than that bound to G-actin, and therefore the local water viscosity is lower around F-actin than around G-actin.
本文报道，聚合形式的肌动蛋白(F-actin)周围的水分子比 G-actin 或在纯水中的水分子更具流动性。使用脉冲场梯度自旋回波(1)H NMR 的测量表明，水在含 F-actin 的水溶液中的自扩散系数随肌动蛋白浓度增加约 5%，而在 G-actin 溶液中接近纯水的自扩散系数。这表明 F-actin/水相互作用是导致水高自扩散的原因。还通过荧光测量研究了肌动蛋白周围的局部粘度，该荧光测量使用荧光染料 Cy3 与肌动蛋白的 Cys 374 缀合。Cy3 连接到 F-actin 上的稳态荧光各向异性为 0.270，低于 G-actin 的 0.334。考虑到 Cy3 与肌动蛋白结合的荧光寿命，它们的旋转相关时间估计分别为 3.8 和 9.1ns，用于 F-和 G-actin。这表明与 G-actin 结合的 Cy3 比与 F-actin 结合的 Cy3 旋转更自由，因此 F-actin 周围的局部水粘度低于 G-actin 周围的局部水粘度。
