美国加州大学Ribbe, Markus W.团队用亚硒酸盐和碲酸盐追踪固氮酶辅因子前体中“第九硫”的插入。相关研究成果发表在2021年10月11日出版的《自然—化学》。

钼固氮酶在其辅因子处催化N₂还原为NH₃，该辅因子是在插入钼和高柠檬酸盐之前通过形成[Fe8S9C]L^-簇合成的[（R-高柠檬酸盐）MoFe7S9C]簇。研究人员之前已经确定了一个[Fe8S8C]L*-簇，该簇与L-簇的核心结构同源，但在带区缺少“第九硫”。然而，“第九硫”插入后L*到L^-簇转化的直接证据和机理细节仍然难以捉摸。

该文中，研究人员使用SeO32和TeO32作为“标记”SO32追踪“第九硫”插入。生化、电子顺磁共振和X射线吸收光谱/扩展X射线吸收精细结构研究表明，“第九硫”在辅因子生物合成过程中的簇转移中起作用，同时揭示了Se^2-和Te^2-样物种并入L^-簇。密度泛函理论计算进一步提出了涉及SO32原位还原为S2的一种可能机制，从而表明该反应可用于标记固氮酶机理研究的催化重要带区。

附：英文原文

Title: Tracing the incorporation of the “ninth sulfur” into the nitrogenase cofactor precursor with selenite and tellurite

Author: Tanifuji, Kazuki, Jasniewski, Andrew J., Villarreal, David, Stiebritz, Martin T., Lee, Chi Chung, Wilcoxen, Jarett, Okhi, Yasuhiro, Chatterjee, Ruchira, Bogacz, Isabel, Yano, Junko, Kern, Jan, Hedman, Britt, Hodgson, Keith O., Britt, R. David, Hu, Yilin, Ribbe, Markus W.

Issue&Volume: 2021-10-11

Abstract: Molybdenum nitrogenase catalyses the reduction of N2 to NH3 at its cofactor, an [(R-homocitrate)MoFe7S9C] cluster synthesized via the formation of a [Fe8S9C] L-cluster prior to the insertion of molybdenum and homocitrate. We have previously identified a [Fe8S8C] L*-cluster, which is homologous to the core structure of the L-cluster but lacks the ‘ninth sulfur’ in the belt region. However, direct evidence and mechanistic details of the L*- to L-cluster conversion upon ‘ninth sulfur’ insertion remain elusive. Here we trace the ‘ninth sulfur’ insertion using SeO32 and TeO32 as ‘labelled’ SO32. Biochemical, electron paramagnetic resonance and X-ray absorption spectroscopy/extended X-ray absorption fine structure studies suggest a role of the ‘ninth sulfur’ in cluster transfer during cofactor biosynthesis while revealing the incorporation of Se2- and Te2-like species into the L-cluster. Density functional theory calculations further point to a plausible mechanism involving in situ reduction of SO32 to S2, thereby suggesting the utility of this reaction to label the catalytically important belt region for mechanistic investigations of nitrogenase.

DOI: 10.1038/s41557-021-00799-8

Source: https://www.nature.com/articles/s41557-021-00799-8