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Fate of the (2Fe-2S)2+ cluster of Escherichia coli biotin synthase during reaction:: A Mossbauer characterization
被引:43
作者:
Bui, BTS
Benda, R
Schünemann, V
Florentin, D
Trautwein, AX
Marquet, A
机构:
[1] Univ Paris 06, CNRS, UMR 7613, Lab Chim Organ Biol, F-75252 Paris 05, France
[2] Med Univ Lubeck, Inst Phys, D-23538 Lubeck, Germany
关键词:
D O I:
10.1021/bi034426c
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, the enzyme which catalyzes the last step of the biosynthesis of biotin, contains only (2Fe-2S)(2+) clusters when isolated under aerobic conditions. Previous results showed that reduction by dithionite or photoreduced deazaflavin converts the (2Fe-2S)(2+) to (4Fe-4S)(2+,+). However, until now, no detailed investigation concerning the fate of the (2Fe-2S)(2+) during reduction under assay conditions (NADPH, flavodoxin, flavodoxin reductase) has been realized. Here, we show by Mossbauer spectroscopy on a partially purified fraction overexpressing the enzyme that, in the presence of a S2- source and Fe2+, there is conversion of the predominant (2Fe-2S)(2+) clusters into a 1:1 mixture of (2Fe-2S)(2+) and (4Fe-4S)(2divided by). No change in this cluster composition was observed in the presence of the physiological reducing system. When the reaction was allowed to proceed by addition of the substrate dethiobiotin, the (4Fe-4S)(2+) was untouched whereas the (2Fe-2S)(2+) was degraded into a new species. This is consistent with the hypothesis that the reduced (4Fe-4S) cluster is involved in mediating the cleavage of AdoMet and that the (2Fe-2S)(2+) is the sulfur source for biotin.
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页码:8791 / 8798
页数:8
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