A New Enzyme Family Catalyzing Methyllanthionine Sulfoxide Formation in Anti-phage Lanthipeptides
Year: 2026
Type: preprint
Abstract: Lanthipeptides are one of the largest classes of ribosomally synthesized and post-translationally modified peptides (RiPPs). The coi biosynthetic gene cluster (BGC) from Streptomyces coelicolor A3(2) encodes a canonical class I lanthipeptide dehydratase (CoiB) and cyclase (CoiC), a bifunctional enzyme (CoiS A ) with an O -methyltransferase (MT) and glutamyl lyase (GL) domain, and a protein of unknown function (CoiH). The product of the coi BGC was recently shown to impart anti-phage activity, but its structure is still unresolved. Previous work investigated the regioselectivity of the GL domains in CoiB and CoiS A and the stereochemistry of the cyclized precursor peptide, but the function of CoiH was not addressed. In this study, co-expression of the peptide CoiA1 with CoiBCS A H resulted in a +16 Da addition on the cyclized peptide compared to when CoiH was omitted. LC-MS/MS analysis indicated that this modification occurred in the first thioether ring. A combination of site-directed mutagenesis, comparison of linear and cyclized peptide substrates, hydrogen peroxide (H₂O₂) treatment, and collision-induced dissociation (CID) mass spectrometric analysis suggested that the sulfur atom in the first methyllanthionine was oxidized to a sulfoxide group by CoiH. This hypothesis was confirmed by NMR analysis. CoiH represents a previously uncharacterized oxygenase family catalyzing sulfoxide formation. Structure prediction tools suggest a novel enzyme fold without obvious metal or cofactor binding sites, raising the possibility that CoiH is a cofactor independent oxidation enzyme.
Language: English
Subfield: Pharmacology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
Funder: National Institutes of Health
OpenAlex ID: W7204448273