Hartvig Nóra, Lõrinczy Dénes, Farkas Nelli, Belagyi Joseph
Central Research Laboratory and Institute of Biophysics, School of Medicine, University of Pécs, Hungary.
Eur J Biochem. 2002 Apr;269(8):2168-77. doi: 10.1046/j.1432-1033.2002.02872.x.
Conventional and saturation transfer electron paramagnetic resonance spectroscopy (EPR and ST EPR) was used to study the orientation of probe molecules in muscle fibers in different intermediate states of the ATP hydrolysis cycle. A separate procedure was used to obtain ST EPR spectra with precise phase settings even in the case of samples with low spectral intensity. Fibers prepared from rabbit psoas muscle were labeled with isothiocyanate spin labels at the reactive thiol sites of the catalytic domain of myosin. In comparison with rigor, a significant difference was detected in the orientation-dependence of spin labels in the ADP and adenosine 5'-[beta,gamma-imido]triphosphate (AdoPP[CH2]P) states, indicating changes in the internal dynamics and domain orientation of myosin. In the AdoPP[CH2]P state, approximately half of the myosin heads reflected the motional state of ADP-myosin, and the other half showed a different dynamic state with greater mobility.
采用常规电子顺磁共振光谱和饱和转移电子顺磁共振光谱（EPR和ST EPR）研究了处于ATP水解循环不同中间状态的肌肉纤维中探针分子的取向。即使对于光谱强度较低的样品，也采用了一种单独的方法来获得具有精确相位设置的ST EPR光谱。从兔腰大肌制备的纤维在肌球蛋白催化结构域的反应性巯基位点用异硫氰酸酯自旋标记物进行标记。与僵直状态相比，在ADP和腺苷5'-[β,γ-亚氨基]三磷酸（AdoPP[CH2]P）状态下，自旋标记物的取向依赖性存在显著差异，表明肌球蛋白的内部动力学和结构域取向发生了变化。在AdoPP[CH2]P状态下，大约一半的肌球蛋白头部反映了ADP-肌球蛋白的运动状态，另一半则表现出不同的动态状态，具有更大的流动性。
