title: Metagenome mining reveals polytheonamides as posttranslationally modified ribosomal peptides.
abstract: It is held as a paradigm that ribosomally synthesized peptides and proteins contain only l-amino acids. We demonstrate a ribosomal origin of the marine sponge-derived polytheonamides, exceptionally potent, giant natural-product toxins. Isolation of the biosynthetic genes from the sponge metagenome revealed a bacterial gene architecture. Only six candidate enzymes were identified for 48 posttranslational modifications, including 18 epimerizations and 17 methylations of nonactivated carbon centers. Three enzymes were functionally validated, which showed that a radical S-adenosylmethionine enzyme is responsible for the unidirectional epimerization of multiple and different amino acids. Collectively, these complex alterations create toxins that function as unimolecular minimalistic ion channels with near-femtomolar activity. This study broadens the biosynthetic scope of ribosomal systems and creates new opportunities for peptide and protein bioengineering.
authors.affiliation: Kekulé Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Freeman
authors.forename: Cristian
authors.initials: C
authors.lastname: Gurgui
authors.forename: Maximilian J
authors.initials: MJ
authors.lastname: Helf
authors.forename: Brandon I
authors.initials: BI
authors.lastname: Morinaka
authors.forename: Agustinus R
authors.initials: AR
authors.lastname: Uria
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Oldham
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Sahl
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsunaga
authors.forename: Jörn
authors.initials: J
authors.lastname: Piel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D007473:Ion Channels / Q000096:biosynthesis / Q000378:metabolism*; D008387:Marine Toxins / Q000096:biosynthesis / Q000378:metabolism*; D054892:Metagenome; D008745:Methylation; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism; D047232:Theonella / Q000382:microbiology*
chemical_list: D007473:Ion Channels; D008387:Marine Toxins; D011506:Proteins; D012436:S-Adenosylmethionine