Structural and kinetic studies of imidazole binding to two members of the cytochrome c6 family reveal an important role for a conserved heme pocket residue
Structural and kinetic studies of imidazole binding to two members of the cytochrome c6 family reveal an important role for a conserved heme pocket residue
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咪唑与细胞色素 c6 家族两个成员结合的结构和动力学研究揭示了保守血红素口袋残基的重要作用
DOI：
10.1007/s00775-011-0758-y
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
J. Worrall
中科院分区：
文献类型：
--
作者：
B. Rajagopal;Michael T. Wilson;D. Bendall;C. Howe;J. Worrall
细胞色素c6家族中51位的氨基酸负责调节超过100 mV的血红素中点氧化还原电位。作为本工作的一部分，已确定的X-射线结构的咪唑加合物的光合细胞色素c6 Q51 V变体从Phormidium laminosum。该结构揭示了轴向Met配体与血红素铁解离，但保留在血红素口袋内，并且容纳Met配体的Ω-环通过与咪唑和血红素丙酸酯-6的极性相互作用而稳定。后者是可能的，因为咪唑结合时两种血红素丙酸酯都发生180°旋转。从平衡和动力学研究，在位置51处的瓦尔残基增加了Fe-S（Met）相互作用的稳定性，并且还影响与咪唑结合相关的动力学。在这方面，发现咪唑与拟南芥细胞色素c6 A结合的kobs与咪唑浓度无关，表明结合过程受Met解离速率常数（约1 s-1）限制，拟南芥细胞色素c6 A在相当于光合细胞色素c6的51位的位置处具有瓦尔。对于细胞色素c6 Q51 V变体，咪唑结合被抑制相比，野生型蛋白质和细胞色素c6 A的V52 Q变体被发现很容易结合咪唑。我们的结论是，在位置51/52在细胞色素C6家族的残基类型是另外负责调整血红素铁-甲硫氨酸键的稳定性和铁蛋白折叠与内源性配体结合的动态特性。
The amino acid at position 51 in the cytochrome c6 family is responsible for modulating over 100 mV of heme midpoint redox potential. As part of the present work, the X-ray structure of the imidazole adduct of the photosynthetic cytochrome c6 Q51V variant from Phormidium laminosum has been determined. The structure reveals the axial Met ligand is dissociated from the heme iron but remains inside the heme pocket and the Ω-loop housing the Met ligand is stabilized through polar interactions with the imidazole and heme propionate-6. The latter is possible owing to a 180° rotation of both heme propionates upon imidazole binding. From equilibrium and kinetic studies, a Val residue at position 51 increases the stability of the Fe–S(Met) interaction and also affects the dynamics associated with imidazole binding. In this respect, the kobs for imidazole binding to Arabidopsis thaliana cytochrome c6A, which has a Val at the position equivalent to position 51 in photosynthetic cytochrome c6, was found to be independent of imidazole concentration, indicating that the binding process is limited by the Met dissociation rate constant (about 1 s−1). For the cytochrome c6 Q51V variant, imidazole binding was suppressed in comparison with the wild-type protein and the V52Q variant of cytochrome c6A was found to bind imidazole readily. We conclude that the residue type at position 51/52 in the cytochrome c6 family is additionally responsible for tuning the stability of the heme iron–Met bond and the dynamic properties of the ferric protein fold associated with endogenous ligand binding.
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1.9 A 分辨率下叶绿体细胞色素 c6 的结构：功能性寡聚化的证据。
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发表时间：
1995
期刊：
Journal of molecular biology.
影响因子：
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通过对咪唑与荚膜红杆菌细胞色素 c2 铰链突变体结合的研究揭示了第六配体甲硫氨酸区域的蛋白质动力学。
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发表时间：
2004
期刊：
Biochemistry.
影响因子：
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作者：
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影响因子：
56.9
作者：
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通讯作者：
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