Modulation of the axial water hydrogen-bonding properties by chemical modification of the substrate in resting state, substrate-bound heme oxygenase from Neisseria meningitidis;: Coupling to the distal H-bond network via ordered water molecules
Modulation of the axial water hydrogen-bonding properties by chemical modification of the substrate in resting state, substrate-bound heme oxygenase from Neisseria meningitidis;: Coupling to the distal H-bond network via ordered water molecules
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DOI：
10.1021/ja0578505
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发表时间：
2006-05-17
影响因子：
15
通讯作者：
La Mar, Gerd N.
中科院分区：
文献类型：
--
作者：
Ma, Li-Hua;Liu, Yangzhong;La Mar, Gerd N.
铁，高自旋，静止状态的底物复合物的血红素加氧酶脑膜炎奈瑟氏菌的配位水的氢键已被系统地扰动由可变的吸电子取代基的氯化血红素外围。顺磁各向异性引起的H-1 NMR偶极位移在四种配合物中具有很强的保守性，偶极位移或各向异性的大小按取代基甲酰基<乙烯基<甲基的顺序增加。磁各向异性是轴向的并且通过轴向Fe-His 23键定向，并且虽然各个各向异性具有类似于5%的不确定性，但是Delta（X）（和零场分裂常数，D与Delta（Xax）成比例）的相对值被定义为1%。由可变零场分裂所暗示的轴向场强度的独特变化与轴向水作为更强的H-键供体的预期雅阁，其顺序为氯化血红素取代基甲酰基>乙烯基>甲基。这些结果建立了轴向各向异性（和D）作为一个敏感的探针的H-键合性质的连接水在静止状态，底物复合物的血红素加氧酶。校正所观察到的不稳定的质子化学位移的顺磁影响表明，Gln 49和His 53，一些类似于10埃的铁，感觉在连接的水H-键合到三个nonligated有序的水分子，连接两个侧链的铁配体的变化。目前的结果预示着良好的检测和表征的变化后，在远端的水氢键的突变的残基在远端网络的有序的水分子和强氢键。
The hydrogen bonding of ligated water in ferric, high-spin, resting-state substrate complexes of heme oxygenase from Neisseria meningitidis has been systematically perturbed by variable electron-withdrawing substituents on the hemin periphery. The pattern of H-1 NMR-detected dipolar shifts due to the paramagnetic anisotropy is strongly conserved among the four complexes, with the magnitude of dipolar shifts or anisotropy increasing in the order of substituent formyl < vinyl < methyl. The magnetic anisotropy is axial and oriented by the axial Fe-His23 bond, and while individual anisotropies have uncertainties of similar to 5%, the relative values of Delta(X) (and the zero-field splitting constant, D proportional to Delta(Xax)) are defined to 1%. The unique changes in the axial field strength implied by the variable zero-field splitting are in accord with expectations for the axial water serving as a stronger H-bond donor in the order of hemin substituents formyl > vinyl > methyl. These results establish the axial anisotropy (and D) as a sensitive probe of the H-bonding properties of a ligated water in resting-state, substrate complexes of heme oxygenase. Correction of observed labile proton chemical shifts for paramagnetic influences indicates that Gln49 and His53, some similar to 10 angstrom from the iron, sense the change in the ligated water H-bonding to the three nonligated ordered water molecules that link the two side chains to the iron ligand. The present results augur well for detecting and characterizing changes in distal water H-bonding upon mutagenesis of residues in the distal network of ordered water molecules and strong H-bonds.