title: The radical SAM enzyme AlbA catalyzes thioether bond formation in subtilosin A.
abstract: Subtilosin A is a 35-residue, ribosomally synthesized bacteriocin encoded by the sbo-alb operon of Bacillus subtilis. It is composed of a head-to-tail circular peptide backbone that is additionally restrained by three unusual thioether bonds between three cysteines and the α-carbon of one threonine and two phenylalanines, respectively. In this study, we demonstrate that these bonds are synthesized by the radical S-adenosylmethionine enzyme AlbA, which is encoded by the sbo-alb operon and comprises two [4Fe-4S] clusters. One [4Fe-4S] cluster is coordinated by the prototypical CXXXCXXC motif and is responsible for the observed S-adenosylmethionine cleavage reaction, whereas the second [4Fe-4S] cluster is required for the generation of all three thioether linkages. On the basis of the obtained results, we propose a new radical mechanism for thioether bond formation. In addition, we show that AlbA-directed substrate transformation is leader-peptide dependent, suggesting that thioether bond formation is the first step during subtilosin A maturation.
authors.affiliation: Department of Chemistry-Biochemistry, Philipps-Universität Marburg, Marburg, Germany.
authors.forename: Leif
authors.initials: L
authors.lastname: Flühe
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Knappe
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gattner
authors.forename: Antje
authors.initials: A
authors.lastname: Schäfer
authors.forename: Olaf
authors.initials: O
authors.lastname: Burghaus
authors.forename: Uwe
authors.initials: U
authors.lastname: Linne
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Marahiel
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001430:Bacteriocins / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D003545:Cysteine / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009876:Operon; D010456:Peptides, Cyclic / Q000737:chemistry / Q000378:metabolism*; D010649:Phenylalanine / Q000737:chemistry; D012436:S-Adenosylmethionine / Q000378:metabolism; D013440:Sulfides / Q000737:chemistry*; D013912:Threonine / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D001430:Bacteriocins; D007506:Iron-Sulfur Proteins; D010456:Peptides, Cyclic; D013440:Sulfides; D013912:Threonine; D010649:Phenylalanine; D012436:S-Adenosylmethionine; C047828:sboA protein, Bacillus subtilis; D003545:Cysteine