Nature of the C-Cluster in Ni-contaning carbon monoxide dehydrogenases

Journal Article · Wed Jan 31 04:00:00 EST 1996 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja9528386· OSTI ID:237276

Hu, Z; Muenck, E ^[1]; Spangler, N J; Ludden, P W ^[2]; Anderson, M E; Xia, J; Lindahl, P A ^[3]

---

1. Carnegie Mellon Univ., Pittsburgh, PA (United States)
2. Univ. of Wisconsin, Madison, WI (United States)
3. Texas A&M Univ., College Station, TX (United States)

The C-cluster of carbon monoxide dehydrogenase (CODH) appears to be the active site for the oxidation of CO to CO{sub 2}. We have studied with EPR and Moessbauer spectroscopy the enzymes from Rhodospirillum rubrum (CODH{sub Rr}: to nearly 8 Fe atoms and 1 Ni atom per {alpha}) and Clostridium thermoaceticum (CODH{sub Ct}; nearly 12 Fe atoms and 2 Ni atoms per {alpha}{beta}). The spectroscopic properties of the B-cluster are the same in Ni-deficient, holo-CODH{sub Rr} and CODH{sub Ct}. The precursor to the C-cluster of Ni-deficient CODH{sub Rr}, labeled C{sup *}, is diamagnetic in the [Fe{sub 4}S{sub 4}]{sup 2+} state , but has an S=3/2 spin in the [Fe{sub 4}S{sub 4}]{sup +} form. Upon incorporation of Ni, the properties of the C{sup *}-cluster change substantially. At E`{sub m}=-110 mV, the C-cluster undergoes a 1-electron reduction from the oxidized state, C{sub ox}, to the reduced state, C{sub red1}, which exhibits the g{sub av}=1.82 EPR signal. We present a model that considers a weak exchange interaction (effective coupling constant j) between an S = 1 Ni{sup II} site (zero-field splitting, D) and the S = 1/2 ground state of the [Fe{sub 4}S{sub 4}]{sup +} cluster. This model suggests {vert_bar}j{vert_bar} < 23 cm{sup -}, accounts for the g values of C{sub red1}, and provides an explanation for the unusual g values (g{sub av}= 2.16) reported by S. W. Ragsdale and co-workers for the adducts of CODH{sub Ct} with thiocyanate and cyanate. The coupling model is consistent with {sup 61}Ni EPR studies of CODH. 73 refs., 15 figs., 2 tabs.

• OSTI ID: 237276
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 4 Vol. 118; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
55 BIOLOGY AND MEDICINE
BASIC STUDIES
66 PHYSICS
CARBON
CARBON MONOXIDE
ELECTRON SPIN RESONANCE
ENERGY LEVELS
ENERGY SPECTRA
ENZYMES
NICKEL COMPLEXES
OXIDOREDUCTASES
SOLID CLUSTERS
STRUCTURAL CHEMICAL ANALYSIS