RESUMO
Peptide backbone α-N-methylations change the physicochemical properties of amide bonds to provide structural constraints and other favorable characteristics including biological membrane permeability to peptides. Borosin natural product pathways are the only known ribosomally encoded and posttranslationally modified peptides (RiPPs) pathways to incorporate backbone α-N-methylations on translated peptides. Here we report the discovery of type IV borosin natural product pathways (termed 'split borosins'), featuring an iteratively acting α-N-methyltransferase and separate precursor peptide substrate from the metal-respiring bacterium Shewanella oneidensis. A series of enzyme-precursor complexes reveal multiple conformational states for both α-N-methyltransferase and substrate. Along with mutational and kinetic analyses, our results give rare context into potential strategies for iterative maturation of RiPPs.
Assuntos
Proteínas de Bactérias/metabolismo , Produtos Biológicos/metabolismo , Metiltransferases/metabolismo , Peptídeos/metabolismo , Processamento de Proteína Pós-Traducional , Algoritmos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Sítios de Ligação/genética , Cristalografia por Raios X , Cinética , Metilação , Metiltransferases/química , Metiltransferases/genética , Mutação , Peptídeos/química , Peptídeos/genética , Conformação Proteica , Multimerização Proteica , Ribossomos/genética , Ribossomos/metabolismo , Shewanella/enzimologia , Shewanella/genética , Especificidade por SubstratoRESUMO
Backbone N-methylations impart several favorable characteristics to peptides including increased proteolytic stability and membrane permeability. Nonetheless, amide bond N-methylations incorporated as post-translational modifications are scarce in nature and were first demonstrated in 2017 for a single set of fungal metabolites. Here we expand on our previous discovery of iterative, autocatalytic α- N-methylating precursor proteins in the borosin family of ribosomally encoded peptide natural products. We identify over 50 putative pathways in a variety of ascomycete and basidiomycete fungi and functionally validate nearly a dozen new self-α- N-methylating catalysts. Significant differences in precursor size, architecture, and core peptide properties subdivide this new peptide family into three discrete structural types. Lastly, using targeted genomics, we link the biosynthetic origins of the potent antineoplastic gymnopeptides to the borosin natural product family. This work highlights the metabolic potential of fungi for ribosomally synthesized peptide natural products.
