Solution 1H NMR characterization of substrate-free C. diphtheriae heme oxygenase: Pertinence for determining magnetic axes in paramagnetic substrate complexes
Solution 1H NMR characterization of substrate-free C. diphtheriae heme oxygenase: Pertinence for determining magnetic axes in paramagnetic substrate complexes
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DOI：
10.1016/j.jinorgbio.2010.06.003
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发表时间：
2010-10-01
影响因子：
3.9
通讯作者：
La Mar, Gerd N.
中科院分区：
文献类型：
--
作者：
Du, Zhenming;Unno, Masaki;La Mar, Gerd N.
质子2D NMR被用来确认在溶液中的高度保守的部分的分子结构后，从致病性细菌白喉棒状杆菌，HmuO的血红素加氧酶的底物损失。的结构的保守部分的化学位移进行评估作为参考的偶极位移需要确定的顺磁性磁化率张量，chi，在顺磁性基板复合物的HmuO的方向。结果表明，化学位移的结构保守的部分无底物HmuO作为优秀的参考残基只有小到中等大小的偶极位移的氰化物抑制底物复合物的HmuO，产生的方向志，基本上是相同的常规获得的大偶极位移的基础上的反磁性参考的经验估计。这些抗磁性化学位移的影响，表征的氢键在生理相关的，静止状态，高自旋水复合物进行了讨论。不稳定的质子交换的模式在远端的H-键网络的无底物HmuO允许比较的动态稳定性变化的三级接触在无底物和底物结合的HmuO和相同的复合物的人血红素加氧酶。(c)2010年爱思唯尔公司All rights reserved.
Proton 2D NMR was used to confirm in solution a highly conserved portion of the molecular structure upon substrate loss for the heme oxygenase from the pathogenic bacterium Corynebacterium diphtheriae, HmuO. The chemical shifts for the conserved portion of the structure are assessed as references for the dipolar shifts needed to determine the orientation of the paramagnetic susceptibility tensor, chi, in paramagnetic substrate complexes of HmuO. It is shown that the chemical shifts for the structurally conserved portion of substrate-free HmuO serve as excellent references for residues with only small to moderate sized dipolar shifts in the cyanide-inhibited substrate complex of HmuO, yielding an orientation of chi that is essentially the same as conventionally obtained from large dipolar shifts based on empirical estimates of the diamagnetic reference. The implications of these diamagnetic chemical shifts for characterizing the hydrogen bonding in the physiologically relevant, resting-state, high-spin aquo complex are discussed. The pattern of labile proton exchange in the distal H-bond network of substrate-free HmuO allowed comparison of changes in dynamic stability of tertiary contacts in the substrate-free and substrate-bound HmuO and with the same complexes of human heme oxygenase. (c) 2010 Elsevier Inc. All rights reserved.