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The solution structure of oxidized rat microsomal cytochrome b(5)

机译：氧化大鼠微粒体细胞色素b（5）的溶液结构

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The solution structure of oxidized rat microsomal cytochrome bs has been obtained from H-1 NMR spectra measured at 800 MHz. Tile available assignment has been extended to 78% of the total protons and 95% of the residues. From 1372 meaningful NOEs, a family of 40 structures has been obtained through the program DYANA; 235 pseudocontact shifts have been then added as further constraints, obtaining an essentially similar family of structures. This latter family has been further refined through restrained energy minimization. The final RMSD values with respect to the average structure are 0.58 +/- 0.10 Angstrom and 1.05 +/- 0.11 Angstrom for backbone and heavy atoms, respectively. The high quality of the structure allows meaningful comparisons with the solution structure of the reduced protein, with the X-ray and solution structures of the oxidized bovine isoenzyme, and with the solution structure of the apoprotein. Upon loss of one electron, the heme plane undergoes a change in its orientation, possibly due to the change of the total charge. Propionate 7 appears to have a conformation which is dependent on the oxidation state of the iron. Helices alpha 2 and alpha 4 also experience changes in their average positions in the two oxidation states. Finally, the backbone NHs experience different exchange properties in the two oxidation states. While those present in the beta sheets forming the basis of the heme pocket are nonexchanging in both oxidation states, the NHs in the helices forming the heme-binding pocket are exchanging with the bulk solvent in the oxidized form, indicating larger local mobility in this state, This observation could suggest that, to optimize the electron transfer process, the local mobility should be properly tuned. [References: 91]
机译：氧化的大鼠微粒体细胞色素bs的溶液结构已从在800 MHz下测量的H-1 NMR光谱中获得。瓷砖的可用分配已扩展到总质子的78％和残基的95％。通过DYANA程序，从1372个有意义的NOE中获得了40个结构的家族。然后添加了235个伪接触位移作为进一步的约束，从而获得了基本相似的结构族。通过限制能量的最小化，后一个家族得到了进一步完善。对于骨架和重原子，相对于平均结构的最终RMSD值分别为0.58 +/- 0.10埃和1.05 +/- 0.11埃。高质量的结构可以与还原蛋白的溶液结构，氧化的牛同工酶的X射线和溶液结构以及脱辅基蛋白的溶液结构进行有意义的比较。当失去一个电子时，血红素平面的方向可能发生变化，这可能是由于总电荷的变化所致。丙酸酯7似乎具有取决于铁的氧化态的构象。螺旋α2和α4在两种氧化态下其平均位置也发生变化。最后，主链NHs在两种氧化态下经历不同的交换特性。尽管存在于形成血红素囊袋基础的β片中的那些在两种氧化状态下均不交换，但形成血红素结合囊袋的螺旋中的NHs与氧化形式的本体溶剂交换，表明在此状态下较大的局部迁移率，该观察结果表明，为了优化电子转移过程，应该适当地调节局部迁移率。 [参考：91]

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