Howard Hughes Medical Institute and Division of Chemistry and Chemical Engineering, MailCode 114-96, California Institute of Technology, Pasadena, CA 91125, USA.
Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany. BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany.
Science. 2014 Sep 26;345(6204):1620-3. doi: 10.1126/science.1256679.
The mechanism of nitrogenase remains enigmatic, with a major unresolved issue concerning how inhibitors and substrates bind to the active site. We report a crystal structure of carbon monoxide (CO)-inhibited nitrogenase molybdenum-iron (MoFe)-protein at 1.50 angstrom resolution, which reveals a CO molecule bridging Fe2 and Fe6 of the FeMo-cofactor. The μ2 binding geometry is achieved by replacing a belt-sulfur atom (S2B) and highlights the generation of a reactive iron species uncovered by the displacement of sulfur. The CO inhibition is fully reversible as established by regain of enzyme activity and reappearance of S2B in the 1.43 angstrom resolution structure of the reactivated enzyme. The substantial and reversible reorganization of the FeMo-cofactor accompanying CO binding was unanticipated and provides insights into a catalytically competent state of nitrogenase.
固氮酶的作用机制仍然扑朔迷离，其中一个主要的未解问题是抑制剂和底物如何与活性位点结合。我们报告了一氧化碳（CO）抑制的固氮酶钼铁（MoFe）-蛋白的晶体结构，分辨率为 1.50 埃，其中揭示了一个 CO 分子桥接 Fe2 和 Fe6 的 FeMo-辅因子。μ2 结合几何结构是通过取代一个带硫原子（S2B）实现的，突出了由于硫的位移而产生的反应性铁物种。CO 抑制是完全可逆的，正如酶活性的恢复和在重新激活酶的 1.43 埃分辨率结构中 S2B 的重新出现所证实的那样。伴随着 CO 结合的 FeMo-辅因子的大量和可逆重组是出乎意料的，为固氮酶的催化能力状态提供了深入了解。
