Spectroelectrochemical characterization of the metal centers in carbon monoxide dehydrogenase (CODH) and nickel-deficient CODH from Rhodospirillum rubrum.
Carbon-monoxide dehydrogenase (CODH) from Rhodospirillum rubrum contains two metal centers: a Ni-X-[Fe4S4]2+/1+ cluster (C-center) that serves as the COoxidation site and a standard [Fe4S4]2+/1+ cluster (B-center) that mediates electron flow from the C-center to external electron acceptors. Four states of the C-center were previously identified in electron paramagnetic resonance (EPR) and Mössbauer studies. In this report, EPR-redox titrations demonstrate that the fully oxidized, diamagnetic form of the C-center (Cox) undergoes a one-electron reduction to the Cred1 state (gav = 1.87) with a midpoint potential of -110 mV. The reduction of Cox to Cred1 is shown to coincide with the reduction of an [Fe4S4]2+/1+ cluster in redox-titration experiments monitored by UV-visible spectroscopy. Nickel-deficient CODH, which is devoid of nickel yet contains both [Fe4S4]2+/1+ clusters, does not exhibit EPR-active states or reduced Fe4S4 clusters at potentials more positive than -350 mV.
Spangler
N J
NJ
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706, USA.
Lindahl
P A
PA
Bandarian
V
V
Ludden
P W
PW
D000445:Aldehyde Oxidoreductases / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D009097:Multienzyme Complexes / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry; D010084:Oxidation-Reduction; D012247:Rhodospirillum rubrum / Q000201:enzymology*; D013056:Spectrophotometry, Ultraviolet
D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; D009532:Nickel; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase