The vanadium- and molybdenum-containing nitrogenases of Azotobacter chroococcum. Comparison of mid-point potentials and kinetics of reduction by sodium dithionite of the iron proteins with bound magnesium adenosine 5′-diphosphate
| Autor: | R N F Thorneley, J Bergström, R R Eady |
|---|---|
| Rok vydání: | 1988 |
| Předmět: |
Flavodoxin
Inorganic chemistry chemistry.chemical_element Electron donor Dithionite medicine.disease_cause Biochemistry Sodium dithionite chemistry.chemical_compound Metalloproteins Nitrogenase medicine Magnesium Molecular Biology Molybdenum biology Chemistry Osmolar Concentration Vanadium Cell Biology Adenosine Diphosphate Isoenzymes Kinetics Crystallography Azotobacter biology.protein Azotobacter chroococcum Oxidation-Reduction Research Article |
| Zdroj: | Europe PubMed Central |
| ISSN: | 1470-8728 0264-6021 |
| DOI: | 10.1042/bj2510165 |
| Popis: | The mid-point potentials of the Fe protein components (Ac2 and Ac2* respectively) of the Mo nitrogenase and V nitrogenase from Azotobacter chroococcum were determined in the presence of MgADP to be −450 mV (NHE) [Ac2(MgADP)2-Ac2*ox.(MgADP)2 couple] and −463 mV (NHE) [Ac2* (MgADP)2-Ac2*ox.(ADP)2 couple] at 23 degrees C at pH 7.2. These values are consistent with a flavodoxin characterized by Deistung & Thorneley [(1986) Biochem. J. 239, 69-75] with Em = −522 mV (NHE) being an effective electron donor to both the Mo nitrogenase and the V nitrogenase in vivo. Ac2*ox.(MgADP)2 and Ac2*ox.(MgADP)2 were reduced by SO2.- (formed by the predissociation of dithionite ion, S2O4(2-)) at similar rates, k = 4.7 × 10(6) +/- 0.5 × 10(6) M-1.s-1 and 3.2 × 10(6) +/- 0.2 × 10(6) M-1.s-1 respectively, indicating structural homology at the electron-transfer site associated with the [4Fe-4S] centre in these proteins. |
| Databáze: | OpenAIRE |
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