Redox intermediates of Desulfovibrio gigas (NiFe) hydrogenase generated under hydrogen

Journal Article · Thu Oct 05 04:00:00 EDT 1989 · Journal of Biological Chemistry; (United States)

OSTI ID:5702967

Teixeira, M; Moura, I; Xavier, A V; Moura, J J.G. ^[1]; LeGall, J; DerVartanian, D V; Peck, Jr, H D ^[2]; Huynh, B H ^[3]

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1. Centro de Quimica Estrutural, Lisboa (Portugal) Univ. Nova de Lisboa (Portugal)
2. Univ. of Georgia, Athens (United States)
3. Emory Univ., Atlanta, GA (United States)

The hydrogenase of Desulfovibrio gigas is a complex enzyme containing one nickel center, one (3Fe-4S) and two (4Fe-4S) clusters. Redox intermediates of this enzyme were generated under hydrogen using a redox-titration technique and were studied by EPR and Moessbauer spectroscopy. In the oxidized states, the two (4Fe-4S){sup 2+} clusters exhibit a broad quadrupole doublet with parameters typical for this type of cluster. Upon reduction, the two (4Fe-4S){sup 1+} clusters are spectroscopically distinguishable, allowing the determination of their midpoint redox potentials. The cluster with higher midpoint potential was labeled Fe-S center 1 and the other with lower potential, Fe-S center 2. The following two EPR signals observed at the weak-field region were tentatively attributed to the reduced (3Fe-4S) cluster: (1) a signal with crossover point at g {approximately} 12, labeled the g = 12 signal, and (2) a broad signal at the very weak-field region ({approximately}3 mT), labeled the Fe-S signal B. The midpoint redox potential associated with the appearance of the g = 12 signal was determined to be {minus}70 {plus minus} 10 mV. At potentials below {minus}250 mV, the g = 12 signal began to decrease in intensity, and simultaneously, the Fe-S signal B appeared. The transformation of the g = 12 signal into the Fe-S signal B was found to parallel the reduction of the two (4Fe-4S) clusters indicating that the (3Fe-4S){sup 0} cluster is sensitive to the redox state of the (4Fe-4S) clusters. Detailed redox profiles for the previously reported Ni-signal C and the g = 2.21 signal were obtained in this study, and evidence was found to indicate that these two signals represent two different oxidation states of the enzyme. Finally, the mechanistic implications of the authors' results are discussed.

• OSTI ID: 5702967
• Journal Information: Journal of Biological Chemistry; (United States), Journal Name: Journal of Biological Chemistry; (United States) Vol. 264:28; ISSN JBCHA; ISSN 0021-9258
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
BIOCHEMISTRY
CHEMICAL COMPOSITION
CHEMISTRY
DESULFOVIBRIO
ELECTRON SPIN RESONANCE
ELEMENTS
ENZYMES
HYDROGEN
HYDROGENASES
MAGNETIC RESONANCE
MICROORGANISMS
NONMETALS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PARTIAL PRESSURE
PROTEINS
REDOX POTENTIAL
RESONANCE
SULFATE-REDUCING BACTERIA