Iron-sulfur center of biotin synthase and lipoate synthase

被引:88
作者
Ollagnier-de Choudens, S
Sanakis, Y
Hewitson, KS
Roach, P
Baldwin, JE
Münck, E
Fontecave, M
机构
[1] Univ Grenoble 1, CNRS, CEA, CB,DBMS,Lab Chim & Biochim,Ctr Redox Biol, F-38054 Grenoble 09, France
[2] Carnegie Mellon Univ, Pittsburgh, PA 15213 USA
[3] Oxford Ctr Mol Sci, Dyson Perrins Lab, Oxford OX1 3QY, England
关键词
D O I
10.1021/bi992090u
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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 Mossbauer studies of Fe-57-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 If oxidation states. The Mossbauer and EPR parameters were Delta E-q = 1.13 mm/s and delta = 0.44 mm/s for the diamagnetic (4Fe-4S)(1+) and Delta E-q = 0.51 mm/s, delta = 0.85 mm/s, delta = 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 [Delta E-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.
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收藏
页码:4165 / 4173
页数:9
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