New mechanistic insights from structural studies of the oxygen-sensing domain of Bradyrhizobium japonicum FixL
New mechanistic insights from structural studies of the oxygen-sensing domain of Bradyrhizobium japonicum FixL
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DOI：
10.1021/bi992346w
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发表时间：
2000-04-11
期刊：
影响因子：
2.9
通讯作者：
Chan, MK
中科院分区：
文献类型：
--
作者：
Gong, WM;Hao, B;Chan, MK
在根瘤菌的FixL/FixJ双组分系统中，FixL血红素结构域充当双氧开关。最近的结构研究慢生型大豆根瘤菌FixL血红素域（BjFixLH）提出了一个变构机制，这是不同于经典的血红蛋白模型。为了进一步深入了解FixL传感机制，已确定BjFixLH与双氧、咪唑和一氧化氮结合的结构。这些结构，特别是结合到其生理配体，双氧的BjFixLH的结构，有助于解决一些重要的问题，相关的BjFixLH传感机制。在氧-BjFixLH结构的基础上，发现保守的精氨酸以使人想起经典肌红蛋白和血红蛋白中的远端组氨酸的模式稳定双氧配体。结合咪唑的BjFixLH的结构阐明了容纳空间体积庞大的配体的结构要求，最后，结合一氧化氮的BjFixLH的结构提供了证据，血红素驱动的构象变化的结构中间体。
The FixL heme domain serves as the dioxygen switch in the FixL/FixJ two-component system of Rhizobia. Recent structural studies of the Bradyrhizobium japonicum FixL heme domain (BjFixLH) have suggested an allosteric mechanism that is distinct from the classical hemoglobin model. To gain further insight into the FixL sensing mechanism, structures of BjFixLH bound to dioxygen, imidazole, and nitric oxide have been determined. These structures, particularly the structure of BjFixLH bound to its physiological ligand, dioxygen, have helped to address a number of important issues relevant to the BjFixLH sensing mechanism. On the basis of the oxy-BjFixLH structure, a conserved arginine is found to stabilize the dioxygen ligand in a mode reminiscent of the distal histidine in classical myoglobins and hemoglobins. The structure of BjFixLH bound to imidazole elucidates the structural requirements for accommodating sterically bulky ligands, Finally, the structure of BjFixLH bound to nitric oxide provides evidence for a structural intermediate in the heme-driven conformational change.