NMR spectroscopy and molecular modelling studies of nitrosylcobalamin: further evidence that the deprotonated, base-off form is important for nitrosylcobalamin in solution.
NMR spectroscopy and molecular modelling studies of nitrosylcobalamin: further evidence that the deprotonated, base-off form is important for nitrosylcobalamin in solution.
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DOI：
10.1039/b810895a
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发表时间：
2009-01-21
期刊：
影响因子：
--
通讯作者：
Brasch NE
中科院分区：
文献类型：
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作者：
Hassanin HA;Hannibal L;Jacobsen DW;Brown KL;Marques HM;Brasch NE
通过 NMR 光谱研究了溶液中亚硝酰钴胺 (NOCbl) 的结构，并指定了 1H 和 13C NMR 光谱。 13C 和 31P NMR 化学位移、NOCbl 的 UV-vis 光谱以及观察到的 NOCbl 的 pK 基础值 ~5.1 提供了证据，表明很大一部分 NOCbl 存在于溶液中的基础 5,6-二甲基苯并咪唑 (DMB) 去质子化形式中。基于 NOCbl 的 NOE 约束分子力学建模给出了退火结构，与 X 射线结构相比，柔性侧链和核苷酸环位置具有较小的构象差异。 300 K 下的分子动力学模拟表明，DMB 仍然紧邻 NOCbl 碱基关闭形式的 Corrin α 面。模拟退火计算产生了 NOCbl 的两种主要构象。第一个例子中，DMB 垂直于 Corrin，其 B3 氮距离金属离子约 3.1 Å，并直接指向金属离子；在第二个中，DMB 与 Corrin 的 D 环平行并隐藏在 D 环下方。
The structure of nitrosylcobalamin (NOCbl) in solution has been studied by NMR spectroscopy and the 1H and 13C NMR spectra have been assigned. 13C and 31P NMR chemical shifts, the UV-vis spectrum of NOCbl and the observed pK base-off value of ~5.1 for NOCbl provide evidence that a significant fraction of NOCbl is present in the base-off, 5,6-dimethylbenzimidazole (DMB) deprotonated, form in solution. NOE-restrained molecular mechanics modelling of base-on NOCbl gave annealed structures with minor conformational differences in the flexible side chains and the nucleotide loop position compared with the X-ray structure. A molecular dynamics simulation at 300 K showed that DMB remains in close proximity to the α face of the corrin in the base-off form of NOCbl. Simulated annealing calculations produced two major conformations of base-off NOCbl. In the first, the DMB is perpendicular to the corrin and its B3 nitrogen is about 3.1 Å away from and pointing directly at the metal ion; in the second the DMB is parallel to and tucked beneath the D ring of the corrin.