Fate of the (2Fe-2S)2+ cluster of Escherichia coli biotin synthase during reaction: A Mössbauer characterization

Bernadette Tse Sum Bui, Rüdiger Benda, Volker Schünemann, Dominique Florentin, Alfred X. Trautwein*, Andrée Marquet

*Corresponding author for this work
53 Citations (Scopus)


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 Mössbauer 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)2+. 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.

Original languageEnglish
Issue number29
Pages (from-to)8791-8798
Number of pages8
Publication statusPublished - 29.07.2003


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