Einsle Oliver
Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg im Breisgau, Germany.
Curr Opin Struct Biol. 2023 Dec;83:102719. doi: 10.1016/j.sbi.2023.102719. Epub 2023 Oct 4.
In providing bioavailable nitrogen as building blocks for all classes of biomacromolecules, biological nitrogen fixation is an essential process for all organismic life. Only a single enzyme, nitrogenase, performs this task at ambient conditions and with ATP as an energy source. The assembly of the complex iron-sulfur enzyme nitrogenase and its catalytic mechanism remains a matter of intense study. Recent progress in the structural analysis of the three known isoforms of nitrogenase-differentiated primarily by the heterometal in their active site cofactor-has revealed a degree of structural plasticity of these clusters that suggest two distinct binding sites for substrates and reaction intermediates. A mechanistic proposal based on this finding integrates most of the available experimental data. Furthermore, the first applications of high-resolution cryo-electron microscopy have highlighted further dynamic conformational changes. Structures obtained under turnover conditions support the proposed alternating half-site reactivity in the C-symmetric nitrogenase complex.
生物固氮为所有生物大分子类别提供可生物利用的氮作为构建模块，是所有生物生命的一个基本过程。在环境条件下且以ATP作为能源时，只有一种酶——固氮酶执行这项任务。复杂的铁硫酶固氮酶的组装及其催化机制仍是深入研究的课题。主要根据其活性位点辅因子中的异金属区分的三种已知固氮酶同工型的结构分析最近取得的进展，揭示了这些簇的一定程度的结构可塑性，这表明存在两个不同的底物和反应中间体结合位点。基于这一发现的机理提议整合了大部分现有实验数据。此外，高分辨率冷冻电子显微镜的首次应用突出了进一步的动态构象变化。在周转条件下获得的结构支持所提出的C对称固氮酶复合物中的交替半位点反应性。
