Genome mining of sulfonated lanthipeptides reveals unique cyclic peptide sulfotransferases

Although sulfonation plays crucial roles in various biological processes and is frequently utilized in medicinal chemistry to improve water solubility and chemical diversity of drug leads,it is rare and underexplored in ribosomally synthesized and post-translationally modified peptides(RiPPs).Biosynthesis of RiPPs typically entails modification of hydrophilic residues,which substantially increases their chemical stability and bioactivity,albeit at the expense of reducing water solubility.To explore sulfonated RiPPs that may have improved solubility,we conducted co-occurrence analysis of RiPP class-defining enzymes and sulfotransferase(ST),and discovered two distinctive biosynthetic gene clusters(BGCs)encoding both lanthipeptide synthetase(LanM)and ST.Upon expressing these BGCs,we characterized the structures of novel sulfonated lanthipeptides and determined the catalytic details of LanM and ST.We demonstrate that SslST-catalyzed sulfonation is leader-independent but relies on the presence of A ring formed by LanM.Both LanM and ST are promiscuous towards residues in the A ring,but ST displays strict regioselectivity toward Tyr5.The recognition of cyclic peptide by ST was further discussed.Bioactivity evaluation underscores the significance of the ST-catalyzed sulfonation.This study sets up the starting point to engineering the novel lanthipeptide STs as biocatalysts for hydrophobic lanthipeptides improvement.

Discovery of daspyromycins A and B,2-aminovinyl-cysteine containing lanthipeptides,through a genomics-based approach

Lanthipeptides are one of the largest groups of ribosomally synthesized and post-translationally modified peptides(RiPPs)and are characterized by the presence of lanthionine(Lan)or methyllanthionine residues(MeLan).Only very few lanthipeptides contain a C-terminal 2-aminovinyl-cysteine(AviCys)motif,but all of them show potent antibacterial activities.Recent advances of genome sequencing led to the rapid accumulation of new biosynthetic gene clusters(BGCs)for lanthipeptides.In this study,through our genome mining strategy,we found the AviCys containing lanthipeptides are widespread in the bacterial kingdom.A lanthipeptide-type biosynthetic gene cluster was identified from public bacterial genome database.Two new lanthipeptides,daspyromycins A and B(1 and 2)containing AviCys motif,along with two degraded products,daspyromycins C and D(3 and 4),were obtained after heterologous expression of the gene cluster in Streptomyces albus J1074.Daspyromycins A and B showed potent antimicrobial activity against a spectrum of Gram-positive and-negative bacteria including methicillin-resistant Staphylococcus aureus(MRSA)and vancomycin-resistant Enterococci(VRE).

Genome Mining and Biosynthesis Study of a Type B Linaridin Reveals a Highly Versatileα-N-Methyltransferase

Linaridins are a small but growing family of natural products belonging to the ribosomally synthesized and post-translationally modified peptide(RiPP)superfamily.In this study,a genome mining approach led to the identification of a novel linaridin,mononaridin(MON),from Streptomyces monomycini.In-frame deletion genetic knockout studies showed that,in addition to many genes essential for MON biosynthesis,monM encodes an S-adenosyl methionine(SAM)-dependentα-N-methyltransferase that is responsible for installing two methyl groups in the MON N-terminus.Besides SAM,MonM also accepts ethyl-SAM and allyl-SAM,in which the methyl of SAM is replaced by an ethyl and an allyl,respectively.We showed that ethyl-SAM and allyl-SAM have distinct reactivities in MonM catalysis,and this observation was further investigated in detail by density functional theory(DFT)calculations.Remarkably,MonM acts efficiently on nisin,a prototypic lantibiotic that is structurally very different from the native substrate,and the ability of MonM to transfer an allyl group to the nisin N-terminus allowed production of a fluorescently labeled nisin,which can be further used in microscopic cell analysis.Our studies provide new insights into linaridin biosynthesis and demonstrate the potential of linaridin methyltransferases in bioengineering applications.