Biochemical and Spectroscopic Characterization of a Radical S‑Adenosyl‑l‑methionine Enzyme Involved in the Formation of a Peptide Thioether Cross-Link

• Published in: Biochemistry (Easton) Vol. 55; no. 14; pp. 2122 - 2134
• Main Authors: Bruender, Nathan A, Wilcoxen, Jarett, Britt, R. David, Bandarian, Vahe
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12.04.2016
• Subjects: Amino Acid Motifs; Amino Acid Substitution; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biocatalysis; Computational Biology; Cysteine - metabolism; Cystine - metabolism; Iron-Sulfur Proteins - chemistry; Iron-Sulfur Proteins - genetics; Iron-Sulfur Proteins - metabolism; Models, Molecular; Mutagenesis, Site-Directed; Mutation; Oxidation-Reduction; Oxidoreductases Acting on Sulfur Group Donors - chemistry; Oxidoreductases Acting on Sulfur Group Donors - genetics; Oxidoreductases Acting on Sulfur Group Donors - metabolism; Peptide Fragments - metabolism; Protein Processing, Post-Translational; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; S-Adenosylmethionine - metabolism; Substrate Specificity; Thermoanaerobacter - enzymology
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/acs.biochem.6b00145

Peptide-derived natural products are a class of metabolites that afford the producing organism a selective advantage over other organisms in their biological niche. While the polypeptide antibiotics produced by the nonribosomal polypeptide synthetases (NRPS) are the most widely recognized, the ribosomally synthesized and post-translationally modified peptides (RiPPs) are an emerging group of natural products with diverse structures and biological functions. Both the NRPS derived peptides and the RiPPs undergo extensive post-translational modifications to produce structural diversity. Here we report the first characterization of the six cysteines in forty-five (SCIFF) [Haft, D. H. and Basu M. K. (2011) J. Bacteriol. 193, 2745–2755] peptide maturase Tte1186, which is a member of the radical S-adenosyl-l-methionine (SAM) superfamily. Tte1186 catalyzes the formation of a thioether cross-link in the peptide Tte1186a encoded by an orf located upstream of the maturase, under reducing conditions in the presence of SAM. Tte1186 contains three [4Fe-4S] clusters that are indispensable for thioether cross-link formation; however, only one cluster catalyzes the reductive cleavage of SAM. Mechanistic imperatives for the reaction catalyzed by the thioether forming radical SAM maturases will be discussed.