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Reversible inactivation of CO dehydrogenase with thiol compounds

DOI: 10.1016/j.bbrc.2014.03.147 DOI Help

Authors: Oliver Kreß (University of Bayreuth) , Manuel Gnida (University of Paderborn) , Astrid M. Pelzmann (University of Bayreuth) , Christian Marx (Friedrich-Schiller-University of Jena) , Wolfram Meyer-klaucke (University Paderborn) , Ortwin Meyer (University of Bayreuth)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical And Biophysical Research Communications , VOL 447 (3) , PAGES 413 - 418

State: Published (Approved)
Published: May 2014
Diamond Proposal Number(s): 8328

Open Access Open Access

Abstract: Carbon monoxide dehydrogenase (CO dehydrogenase) from Oligotropha carboxidovorans is a structurally characterized member of the molybdenum hydroxylase enzyme family. It catalyzes the oxidation of CO (CO + H2O → CO2 + 2e− + 2H+) which proceeds at a unique [CuSMo(O)OH] metal cluster. Because of changing activities of CO dehydrogenase, particularly in subcellular fractions, we speculated whether the enzyme would be subject to regulation by thiols (RSH). Here we establish inhibition of CO dehydrogenase by thiols and report the corresponding Ki-values (mM): l-cysteine (5.2), d-cysteine (9.7), N-acetyl-l-cysteine (8.2), d,l-homocysteine (25.8), l-cysteine–glycine (2.0), dithiothreitol (4.1), coenzyme A (8.3), and 2-mercaptoethanol (9.3). Inhibition of the enzyme was reversed by CO or upon lowering the thiol concentration. Electron paramagnetic resonance spectroscopy (EPR) and X-ray absorption spectroscopy (XAS) of thiol-inhibited CO dehydrogenase revealed a bimetallic site in which the RSH coordinates to the Cu-ion as a third ligand {[MoVI(O)OH(2)SCuI(SR)S-Cys]} leaving the redox state of the Cu(I) and the Mo(VI) unchanged. Collectively, our findings establish a regulation of CO dehydrogenase activity by thiols in vitro. They also corroborate the hypothesis that CO interacts with the Cu-ion first. The result that thiol compounds much larger than CO can freely travel through the substrate channel leading to the bimetallic cluster challenges previous concepts involving chaperone function and is of importance for an understanding how the sulfuration step in the assembly of the bimetallic cluster might proceed.

Journal Keywords: Carbon Monoxide Dehydrogenase Regulation; Oligotropha Carboxidovorans; Thiol; Molybdenum; Copper; X-Ray Absorption Spectroscopy

Subject Areas: Biology and Bio-materials

Instruments: B18-Core EXAFS