Correlating Conformational Equilibria with Catalysis in the Electron Bifurcating EtfABCX of Thermotoga maritima.
Correlating Conformational Equilibria with Catalysis in the Electron Bifurcating EtfABCX of Thermotoga maritima.
复制标题
DOI：
10.1021/acs.biochem.3c00472
复制
发表时间：
2024-01-02
期刊：
影响因子：
2.9
通讯作者：
Hura, Greg L.
中科院分区：
文献类型：
--
作者：
Murray, Daniel T.;Ge, Xiaoxuan;Schut, Gerrit J.;Rosenberg, Daniel J.;Hammel, Michal;Bierma, Jan C.;Hille, Russ;Adams, Michael W. W.;Hura, Greg L.
电子分叉(BF)是厌氧菌中一种古老的能量耦合机制，其相关的酶机制至今仍是个谜。在BF黄素酶中，化学上的高势电子以热力学上有利的方式形成，通过同时降低第二个电子的势能，然后将其提供给生理受体。对来自Thermotoga maritima的BF-酶Fix/EtfABCX的冷冻-EM和光谱分析表明，BF-酶含有一个特殊的黄素腺嘌呤二核苷酸，当它被NADH还原时，一个低势电子转移到铁氧还蛋白，一个高势电子还原孟喹酮。高能中间体的能量转移必须在构象上仔细安排，以避免平衡。在这里，厌氧尺寸排除耦合小角X射线散射(SEC-SAXS)表明，包含BF-和电子转移(ET)-黄素的Fix/EtfAB杂二聚体亚复合体存在于黄素结合结构域之间的紧凑态和扩展态的构象平衡中，其丰度受到还原和NAD(H)结合的影响。这些构象确定了与毛滴虫酶相关的动力学，也概括了在同源BF黄素酶的静态结构中确定的状态。单独减少Fix/EtfABCX的黄素不足以引起有利于ET的结构域移动，但需要NAD(H)结合诱导的结构性“触发”。模型表明，Fix/EtfABCX的超二聚体相对于其BF-亚络合物以多种状态存在，这表明超单体之间存在着优化催化的协同机制。构象状态与途径步骤的关联提示了Fix/EtfABCX在其催化循环中进行的一种结构手段。总之，这些观察为追踪Fix/EtfABCX的催化作用提供了一个结构框架。
Electron bifurcation (BF) is an evolutionarily ancient energy coupling mechanism in anaerobes, whose associated enzymatic machinery remains enigmatic. In BF-flavoenzymes, a chemically high-potential electron forms in a thermodynamically favorable fashion by simultaneously dropping the potential of a second electron before its donation to physiological acceptors. The cryo-EM and spectroscopic analyses of the BF-enzyme Fix/EtfABCX from Thermotoga maritima suggest that the BF-site contains a special flavin-adenine dinucleotide and, upon its reduction with NADH, a low-potential electron transfers to ferredoxin and a high-potential electron reduces menaquinone. The transfer of energy from high-energy intermediates must be carefully orchestrated conformationally to avoid equilibration. Herein, anaerobic size exclusion-coupled small-angle X-ray scattering (SEC-SAXS) shows that the Fix/EtfAB heterodimer subcomplex, which houses BF- and electron transfer (ET)-flavins, exists in a conformational equilibrium of compacted and extended states between flavin-binding domains, the abundance of which is impacted by reduction and NAD(H) binding. The conformations identify dynamics associated with the T. maritima enzyme and also recapitulate states identified in static structures of homologous BF-flavoenzymes. Reduction of Fix/EtfABCX’s flavins alone is insufficient to elicit domain movements conducive to ET but requires a structural “trigger” induced by NAD(H) binding. Models show that Fix/EtfABCX’s superdimer exists in a combination of states with respect to its BF-subcomplexes, suggesting a cooperative mechanism between supermonomers for optimizing catalysis. The correlation of conformational states with pathway steps suggests a structural means with which Fix/EtfABCX may progress through its catalytic cycle. Collectively, these observations provide a structural framework for tracing Fix/EtfABCX’s catalysis.
登录
查看更多内容
影响因子：
7.7
作者：
Furlan, Chris;Chongdar, Nipa;Gupta, Pooja;Lubitz, Wolfgang;Ogata, Hideaki;Blaza, James N.;Birrell, James A.
通讯作者：
Birrell, James A.
DOI：
10.1073/pnas.2016978118
发表时间：
2021-01-12
影响因子：
11.1
作者：
Feng, Xiang;Schut, Gerrit J.;Adams, Michael W. W.
通讯作者：
Adams, Michael W. W.
影响因子：
64.8
作者：
Jumper J;Evans R;Pritzel A;Green T;Figurnov M;Ronneberger O;Tunyasuvunakool K;Bates R;Žídek A;Potapenko A;Bridgland A;Meyer C;Kohl SAA;Ballard AJ;Cowie A;Romera-Paredes B;Nikolov S;Jain R;Adler J;Back T;Petersen S;Reiman D;Clancy E;Zielinski M;Steinegger M;Pacholska M;Berghammer T;Bodenstein S;Silver D;Vinyals O;Senior AW;Kavukcuoglu K;Kohli P;Hassabis D
通讯作者：
Hassabis D
影响因子：
6.1
作者：
Konarev, PV;Volkov, VV;Svergun, DI
通讯作者：
Svergun, DI
影响因子：
5.2
作者：
Buckel W;Thauer RK
通讯作者：
Thauer RK