title: Mechanistic insight into the nitrosylation of the [4Fe-4S] cluster of WhiB-like proteins.
abstract: 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 10(4)-fold faster than that observed with O(2) and is by far the most rapid iron-sulfur cluster nitrosylation reaction reported to date. An overall stoichiometry of [Fe(4)S(4)(Cys)(4)](2-) + 8NO → 2[Fe(I)(2)(NO)(4)(Cys)(2)](0) + S(2-) + 3S(0) 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 [Fe(I)(4)(NO)(8)(Cys)(4)](0) derived by dimerization of a pair of Roussin's red ester (RRE) complexes.
authors.affiliation: Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
authors.forename: Jason C
authors.initials: JC
authors.lastname: Crack
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Smith
authors.forename: Melanie R
authors.initials: MR
authors.lastname: Stapleton
authors.forename: Jamie
authors.initials: J
authors.lastname: Peck
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Watmough
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Buttner
authors.forename: Roger S
authors.initials: RS
authors.lastname: Buxton
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Green
authors.forename: Vasily S
authors.initials: VS
authors.lastname: Oganesyan
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Thomson
authors.forename: Nick E
authors.initials: NE
authors.lastname: Le Brun
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002417:Cattle; D007501:Iron / Q000378:metabolism*; D008958:Models, Molecular; D009569:Nitric Oxide / Q000378:metabolism*; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D013455:Sulfur / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D014157:Transcription Factors; C081543:whiB protein, Streptomyces; D009569:Nitric Oxide; D013455:Sulfur; D007501:Iron