S-亚硝基化肌红蛋白的光谱、动力学和水合作用
Spectroscopy, Dynamics and Hydration of S-Nitrosylated Myoglobin
摘要：
S-亚硝基化，即NO共价加成到半胱氨酸的巯基侧链上，是一种重要的后过渡修饰，可以改变各种蛋白质的功能。研究了甲基封端的半胱氨酸模型体系和肌红蛋白在凝聚相中S-亚硝基化的结构动力学和振动光谱。使用传统的点电荷和物理上更现实的多极力场的-SNO组，它被发现，SN-和NO-拉伸和SNO-弯曲振动可以定位和区分从其他蛋白质模式的模拟MbSNO在50 K。稳定的顺式-和反式-MbSNO的发现与对其他蛋白质的实验一致，正如对掩埋的-SNO的观察一样。对于MbSNO，在$\sim 3$的模拟中观察到的EF环的重新定位与可用的X射线结构一致，并且-SNO标记所采用的构象与X射线结构具有良好的总体一致性。尽管-SNO基团的尺寸较大，但由于更强的静电，发现MbSNO在修饰位点的10 μ π ι内比WT Mb募集更多的水分子。类似地，当比较A-和H-螺旋之间的水合时，它们在WT和MbSNO之间相差高达30%。这表明局部水合作用也可以通过亚硝基化进行显著调节。
英文摘要：
S-nitrosylation, the covalent addition of NO to the thiol side chain of cysteine, is an important post-transitional modification that can alter the function of various proteins. The structural dynamics and vibrational spectroscopy of S-nitrosylation in the condensed phase is investigated for the methyl-capped cysteine model system and for myoglobin. Using conventional point charge and physically more realistic multipolar force fields for the -SNO group it is found that the SN- and NO-stretch and the SNO-bend vibrations can be located and distinguished from the other protein modes for simulations of MbSNO at 50 K. The finding of stable cis- and trans-MbSNO is consistent with experiments on other proteins as is the observation of buried -SNO. For MbSNO the observed relocation of the EF loop in the simulations by $\sim 3$ Å\/ is consistent with the available X-ray structure and the conformations adopted by the -SNO label are in good overall agreement with the X-ray structure. Despite the larger size of the -SNO group, MbSNO is found to recruit more water molecules within 10 Å\/ of the modification site than WT Mb due to the stronger electrostatics. Similarly, when comparing the hydration between the A- and H-helices they differ by up to 30 \% between WT and MbSNO. This suggests that local hydration can also be significantly modulated through nitrosylation.
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