title: Two [4Fe-4S] clusters containing radical SAM enzyme SkfB catalyze thioether bond formation during the maturation of the sporulation killing factor.
abstract: The sporulation killing factor (SKF) is a 26-residue ribosomally assembled and posttranslationally modified sactipeptide. It is produced by Bacillus subtilis 168 and plays a key role in its sporulation. Like all sactipeptides, SKF contains a thioether bond, which links the cysteine residue Cys4 with the α-carbon of the methionine residue Met12. In this study we demonstrate that this bond is generated by the two [4Fe-4S] clusters containing radical SAM enzyme SkfB, which is encoded in the skf operon. By mutational analysis of both cluster-binding sites, we were able to postulate a mechanism for thioether generation which is in agreement with that of AlbA. Furthermore, we were able to show that thioether bond formation is specific toward hydrophobic amino acids at the acceptor site. Additionally we demonstrate that generation of the thioether linkage is leader-peptide-dependent, suggesting that this reaction is the first step in SKF maturation.
authors.affiliation: Department of Chemistry/Biochemistry, Philipps-Universität Marburg, Hans-Meerwein Straße 4, D-35043 Marburg, Germany.
authors.forename: Leif
authors.initials: L
authors.lastname: Flühe
authors.forename: Olaf
authors.initials: O
authors.lastname: Burghaus
authors.forename: Beata M
authors.initials: BM
authors.lastname: Wieckowski
authors.forename: Tobias W
authors.initials: TW
authors.lastname: Giessen
authors.forename: Uwe
authors.initials: U
authors.lastname: Linne
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Marahiel
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D055162:Biocatalysis; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D008968:Molecular Conformation; D013440:Sulfides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D013440:Sulfides; C115343:spo0M protein, Bacillus subtilis