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Instruments / Technical Area	Publication Details	Published	Actions
B18-Core EXAFS	Reversible inactivation of CO dehydrogenase with thiol compounds Oliver Kreß , Manuel Gnida , Astrid M. Pelzmann , Christian Marx , Wolfram Meyer-klaucke , Ortwin Meyer Biochemical And Biophysical Research Communications 447 (3), 413 - 418 DOI: 10.1016/j.bbrc.2014.03.147 Diamond Proposal Number(s): [8328] Open Access Show Abstract ▼ 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.	May 2014
I18-Microfocus Spectroscopy	X-ray Absorption Spectroscopy of an Investigational Anticancer Gallium(III) Drug: Interaction with Serum Proteins, Elemental Distribution Pattern, and Coordination of the Compound in Tissue Alfred Hummer , Caroline Bartel , Vladimir B. Arion , Michael A. Jakupec , Wolfram Meyer-klaucke , Tina Geraki , Paul Quinn , Ana Mijovilovich , Bernhard K. Keppler , Annette Rompel Journal Of Medicinal Chemistry 55 (11), 5601 - 5613 DOI: 10.1021/jm3005459 Diamond Proposal Number(s): [6303] Show Abstract ▼ Abstract: Tris(8-quinolinolato)gallium(III) (1, KP46) is a very promising investigational anticancer drug. Its interaction with serum proteins, elemental distribution, and coordination in tissue were investigated with X-ray absorption (XAS) methods. Model compounds with mixed O, N, and/or S donor atoms are reported. The coordination and structure of 1 in cell culture medium (minimum essential medium, MEM) and fetal calf serum (FCS) were probed by XANES and EXAFS. The interaction of 1 with the serum proteins apotransferrin (apoTf) and human serum albumin (HSA) was addressed as well. By application of micro-XAS to tissue samples from mice treated with 1, the gallium distribution pattern was analyzed and compared to those of physiological trace elements. The complex 1 turned out to be very stable under physiological conditions, in cell culture media and in tissue samples. The coordination environment of the metal center remains intact in the presence of apoTf and HSA. The gallium distribution pattern in tumor and liver tissue revealed high similarities to the distribution patterns of Zn and Fe, minor similarities to Cu and Ni, and no similarity to Ca.	Jun 2012

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