Development of photo-driven motor proteins using phtochromic molecules

ATP驱动的马达蛋白质通过像凸轮轴这样的机械系统，将ATP水解产生的化学能转化为物理运动能。将人工能量输入装置引入到马达蛋白的能量转导部位，可以在没有三磷酸腺苷的情况下驱动或调节马达蛋白。在本研究中，由于紫外光(UV)和可见光(VIS)的异构化，光致变色分子可逆地改变了它们的构象，并具有高响应性，被用作能量输入装置。特别是偶氮苯和螺吡喃类化合物，它们在紫外可见光下的异构化特性发生了很大的变化，可能会有效地发挥作用。本研究合成了几种能与半胱氨酸侧链共价结合的偶氮苯和螺吡喃衍生物。还制备了几个在特定部位有一个反应性半胱氨酸的马达蛋白突变体。已有研究表明，对于骨骼肌肌球蛋白运动域，反应性半胱氨酸残基SH1和SH2在偶氮苯衍生物上的异构化引起的局部构象变化引起了杠杆臂部分的摆动。结果表明，掺入的光致变色基团在马达蛋白中起到了机械能输入的作用。这项利用光致变色分子的新技术可能也适用于其他能量传递和调节蛋白质。

ATP driven-motor proteins transduce chemical energy generated from ATP hydrolysis into the physical motion energy with the mechanical system like cam-shaft. It is expected that introduction of artificial energy input device into the energy transducing site of motor protein, enable the driving or regulating of motor proteins without ATP. In the present study, photochromic molecules which change their conformation reversibly with high response due to the isomerization by ultraviolet (UV) and visible light (VIS) irradiation, have been utilized as energy input device. Especially azobenzene and spiropyran derivatives, which change their characteristics dramatically on isomerization by UV-VIS light irradiation, might work effectively.In this study, several kinds of azobenzene and spiropyran derivatives, which can bind to cysteine side chain covalently, have been synthesized. And several motor protein mutants, which have one reactive cysteine at the specific site, have been also prepared. It has been demonstrated that for skeletal muscle myosin motor domain, the localized conformational changes resulting from isomerization on azobenzene derivative cross-linking of reactive cysteine residues, SH1 and SH2 induced swing in the lever arm portion. It was shown that the incorporated photochromic group acts as a mechanical energy input in a motor protein. The new technique using photochromic molecules may be applicable to other energy transducing and regulatory proteins.