Fate of the (2Fe-2S)2+ Cluster of Escherichia coli Biotin Synthase during Reaction: A Mössbauer Characterization
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- 作者：Bernadette Tse Sum Bui ; Rü ; diger Benda ; Volker Schü ; nemann ; Dominique Florentin ; Alfred X. Trautwein ; and André ; e Marquet
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：July 29, 2003
- 年：2003
- 卷：42
- 期：29
- 页码：8791 - 8798
- 全文大小：127K
- 年卷期：v.42,no.29(July 29, 2003)
- ISSN：1520-4995
文摘
Biotin synthase, the enzyme which catalyzes the last step of the biosynthesis of biotin, containsonly (2Fe-2S)2+ clusters when isolated under aerobic conditions. Previous results showed that reductionby 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 Mössbauer spectroscopyon 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)2+. No change in this cluster composition was observed in the presence of the physiological reducingsystem. 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 withthe hypothesis that the reduced (4Fe-4S) cluster is involved in mediating the cleavage of AdoMet andthat the (2Fe-2S)2+ is the sulfur source for biotin.