Mechanistic insight into the nitrosylation of the [4Fe−4S] cluster of WhiB-like proteins

Jason C. Crack, Laura J. Smith, Melanie R. Stapleton, Jamie Peck, Nicholas J. Watmough, Mark J. Buttner, Roger S. Buxton, Jeffrey Green, Vasily S. Oganesyan, Andrew J. Thomson, Nick E. Le Brun

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119 Citations (Scopus)


The reactivity of protein bound iron-sulfur clusters with nitric oxide (NO) is well documented, but little is known about the actual mechanism of cluster nitrosylation. Here, we report studies of members of the Wbl family of [4Fe-4S] containing proteins, which play key roles in regulating developmental processes in actinomycetes, including Streptomyces and Mycobacteria, and have been shown to be NO responsive. Streptomyces coelicolor WhiD and Mycobacterium tuberculosis WhiB1 react extremely rapidly with NO in a multiphasic reaction involving, remarkably, 8 NO molecules per [4Fe-4S] cluster. The reaction is 104-fold faster than that observed with O2 and is by far the most rapid iron-sulfur cluster nitrosylation reaction reported to date. An overall stoichiometry of [Fe4S4(Cys)4]2- + 8NO ? 2[FeI2(NO)4(Cys)2]0 + S2- + 3S0 has been established by determination of the sulfur products and their oxidation states. Kinetic analysis leads to a four-step mechanism that accounts for the observed NO dependence. DFT calculations suggest the possibility that the nitrosylation product is a novel cluster [FeI4(NO)8(Cys)4]0 derived by dimerization of a pair of Roussin’s red ester (RRE) complexes.
Original languageEnglish
Pages (from-to)1112-1121
Number of pages10
JournalJournal of the American Chemical Society
Issue number4
Publication statusPublished - 2011

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