Showing papers by "Ortwin Meyer published in 2004"
TL;DR: The functional cluster A of ACS(Ch) contains a Ni-Ni-[4Fe-4S] site, in which the positions proximal and distal to the cubane are occupied by Ni ions, which is apparent from a positive correlation of the Ni contents and negative correlations of the Cu or Zn contents with the acetyl-CoA/CO exchange activities of different preparations of monomeric ACS.
Abstract: In anaerobic microorganisms employing the acetyl-CoA pathway, acetyl-CoA synthase (ACS) and CO dehydrogenase (CODH) form a complex (ACS/CODH) that catalyzes the synthesis of acetyl-CoA from CO, a methyl group, and CoA. Previously, a [4Fe-4S] cubane bridged to a copper-nickel binuclear site (active site cluster A of the ACS component) was identified in the ACSMt/CODHMt from Moorella thermoacetica whereas another study revealed a nickel-nickel site in the open form of ACSMt, and a zink-nickel site in the closed form. The ACSCh of the hydrogenogenic bacterium Carboxydothermus hydrogenoformans was found to exist as an 82.2-kDa monomer as well as in a 1:1 molar complex with the 73.3-kDa CODHIIICh. Homogenous ACSCh and ACSCh/CODHIIICh catalyzed the exchange between [1-14C]acetyl-CoA and 12CO with specific activities of 2.4 or 5.9 μmol of CO per min per mg, respectively, at 70°C and pH 6.0. They also catalyzed the synthesis of acetyl-CoA from CO, methylcobalamin, corrinoid iron-sulfur protein, and CoA with specific activities of 0.14 or 0.91 μmol of acetyl-CoA formed per min per mg, respectively, at 70°C and pH 7.3. The functional cluster A of ACSCh contains a Ni-Ni-[4Fe-4S] site, in which the positions proximal and distal to the cubane are occupied by Ni ions. This result is apparent from a positive correlation of the Ni contents and negative correlations of the Cu or Zn contents with the acetyl-CoA/CO exchange activities of different preparations of monomeric ACSCh, a 2.2-A crystal structure of the dithionite-reduced monomer in an open conformation, and x-ray absorption spectroscopy.
255 citations
TL;DR: The CO oxidation activity of CODHII(Ch) is determined under different conditions of crystallization, prepared crystals of the enzyme in the presence of dithiothreitol or dithionite as reducing agents under an atmosphere of N(2) or CO, and solved the corresponding structures.
Abstract: During the past two years, crystal structures of Cu- and Mo-containing carbon monoxide dehydrogenases (CODHs) and Ni- and Fe-containing CODHs have been reported. The active site of CODHs from anaerobic bacteria (cluster C) is composed of Ni, Fe, and S for which crystallographic studies of the enzymes from Carboxydothermus hydrogenoformans, Rhodospirillum rubrum, and Moorella thermoacetica revealed structural similarities in the overall protein fold but showed substantial differences in the essential Ni coordination environment. The [Ni−4Fe−5S] cluster C in the fully catalytically competent dithionite-reduced CODH II from C. hydrogenoformans (CODHIICh) at 1.6 A resolution contains a characteristic μ2-sulfido ligand between Ni and Fe1, resulting in a square-planar ligand arrangement with four S-ligands at the Ni ion. In contrast, the [Ni−4Fe−4S] clusters C in CO-treated CODH from R. rubrum resolved at 2.8 A and in CO-treated acetyl-CoA synthase/CODH complex from M. thermoacetica at 2.2 and 1.9 A resolution,...
86 citations