Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom.
Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E5, Canada.
Sci Rep. 2017 May 11;7(1):1757. doi: 10.1038/s41598-017-01840-y.
Arsenite oxidase is thought to be an ancient enzyme, originating before the divergence of the Archaea and the Bacteria. We have investigated the nature of the molybdenum active site of the arsenite oxidase from the Alphaproteobacterium Rhizobium sp. str. NT-26 using a combination of X-ray absorption spectroscopy and computational chemistry. Our analysis indicates an oxidized Mo(VI) active site with a structure that is far from equilibrium. We propose that this is an entatic state imposed by the protein on the active site through relative orientation of the two molybdopterin cofactors, in a variant of the Rây-Dutt twist of classical coordination chemistry, which we call the pterin twist hypothesis. We discuss the implications of this hypothesis for other putatively ancient molybdopterin-based enzymes.
亚砷酸盐氧化酶被认为是一种古老的酶，起源于古菌和细菌的分化之前。我们使用 X 射线吸收光谱和计算化学的组合研究了来自 Alphaproteobacterium Rhizobium sp. str. NT-26 的亚砷酸盐氧化酶的钼活性位点的性质。我们的分析表明，该活性位点具有氧化的 Mo(VI)，其结构远非平衡。我们提出，这是蛋白质通过两个钼喋呤辅因子的相对取向对活性位点施加的紧张状态，这是经典配位化学中 Rây-Dutt 扭曲的一种变体，我们称之为喋呤扭曲假说。我们讨论了这个假说对其他假定的古老钼喋呤基酶的影响。
