PMID:12873140
| Citation |
Tse Sum Bui, B, Benda, R, Schünemann, V, Florentin, D, Trautwein, AX and Marquet, A (2003) Fate of the (2Fe-2S)(2+) cluster of Escherichia coli biotin synthase during reaction: a Mössbauer characterization. Biochemistry 42:8791-8 |
|---|---|
| Abstract |
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 S(2)(-) source and Fe(2+), 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. |
| Links |
PubMed Online version:10.1021/bi034426c |
| Keywords |
Ammonium Sulfate/pharmacology; Dose-Response Relationship, Drug; Escherichia coli/enzymology; Flavin-Adenine Dinucleotide/pharmacology; Iron/metabolism; Models, Chemical; NADP/metabolism; Spectroscopy, Mossbauer/methods; Subcellular Fractions; Sulfur/metabolism; Sulfurtransferases/chemistry |
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