Trinuclear copper biocatalytic center forms an active site of thiocyanate dehydrogenase
Tamara V. Tikhonova (Russian Academy of Sciences)
Dimitry Y. Sorokin (TU Delft - Applied Sciences, Russian Academy of Sciences)
Wilfred R. Hagen (TU Delft - Applied Sciences)
Maria G. Khrenova (Chemistry Faculty of M. V. Lomonosov Moscow State University, Russian Academy of Sciences)
Gerard Muyzer (Universiteit van Amsterdam)
Tatiana V. Rakitina (Russian Academy of Sciences, NRC “Kurchatov Institute”)
Ivan G. Shabalin (University of Virginia Health System)
Anton A. Trofimov (Russian Academy of Sciences)
Stanislav I. Tsallagov (Russian Academy of Sciences)
Vladimir O. Popov (NRC “Kurchatov Institute”, Russian Academy of Sciences)
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Abstract
Biocatalytic copper centers are generally involved in the activation and reduction of dioxygen, with only few exceptions known. Here we report the discovery and characterization of a previously undescribed copper center that forms the active site of a copper-containing enzyme thiocyanate dehydrogenase (suggested EC 1.8.2.7) that was purified from the haloalkaliphilic sulfur-oxidizing bacterium of the genus Thioalkalivibrio ubiquitous in saline alkaline soda lakes. The copper cluster is formed by three copper ions located at the corners of a near-isosceles triangle and facilitates a direct thiocyanate conversion into cyanate, elemental sulfur, and two reducing equivalents without involvement of molecular oxygen. A molecular mechanism of catalysis is suggested based on high-resolution three-dimensional structures, electron paramagnetic resonance (EPR) spectroscopy, quantum mechanics/molecular mechanics (QM/MM) simulations, kinetic studies, and the results of site-directed mutagenesis.