| Autor: |
Ollagnier-De Choudens S; Laboratoire de Chimie et Biochimie des Centres Rédox Biologiques, DBMS-CB, CEA/CNRS/Université Joseph Fourier, 17 Avenue des Martyrs, 38054 Grenoble Cedex 09, France., Sanakis Y, Hewitson KS, Roach P, Baldwin JE, Münck E, Fontecave M |
| Jazyk: |
angličtina |
| Zdroj: |
Biochemistry [Biochemistry] 2000 Apr 11; Vol. 39 (14), pp. 4165-73. |
| DOI: |
10.1021/bi992090u |
| Abstrakt: |
Biotin synthase and lipoate synthase are homodimers that are required for the C-S bond formation at nonactivated carbon in the biosynthesis of biotin and lipoic acid, respectively. Aerobically isolated monomers were previously shown to contain a (2Fe-2S) cluster, however, after incubation with dithionite one (4Fe-4S) cluster per dimer was obtained, suggesting that two (2Fe-2S) clusters had combined at the interface of the subunits to form the (4Fe-4S) cluster. Here we report Mössbauer studies of (57)Fe-reconstituted biotin synthase showing that anaerobically prepared enzyme can accommodate two (4Fe-4S) clusters per dimer. The (4Fe-4S) cluster is quantitatively converted into a (2Fe-2S)(2+) cluster upon exposure to air. Reduction of the air-exposed enzyme with dithionite or photoreduced deazaflavin yields again (4Fe-4S) clusters. The (4Fe-4S) cluster is stable in both the 2+ and 1+ oxidation states. The Mössbauer and EPR parameters were DeltaE(q) = 1.13 mm/s and delta = 0.44 mm/s for the diamagnetic (4Fe-4S)(2+) and DeltaE(q) = 0.51 mm/s, delta = 0.85 mm/s, g(par) = 2.035, and g(perp) = 1.93 for the S = (1)/(2) state of (4Fe-4S)(1+). Considering that we find two (4Fe-4S) clusters per dimer, our studies argue against the early proposal that the enzyme contains one (4Fe-4S) cluster bridging the two subunits. Our study of lipoate synthase gave results similar to those obtained for BS: under strict anaerobiosis, lipoate synthase can accommodate a (4Fe-4S) cluster per subunit [DeltaE(q) = 1.20 mm/s and delta = 0.44 mm/s for the diamagnetic (4Fe-4S)(2+) and g(par) = 2.039 and g(perp) = 1.93 for the S = (1)/(2) state of (4Fe-4S)(1+)], which reacts with oxygen to generate a (2Fe-2S)(2+) center. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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