Genome-Guided Discovery of the First Myxobacterial Biarylitide Myxarylin Reveals Distinct C-N Biaryl Crosslinking in RiPP Biosynthesis.

Joachim J Hug,Fabian Panter,Petra Šenica,Christine Walt,Rolf Müller,Nicolas A Frank

doi:10.3390/molecules26247483

Abstract

Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a structurally diverse group of natural products. They feature a wide range of intriguing post-translational modifications, as exemplified by the biarylitides. These are a family of cyclic tripeptides found in Planomonospora, carrying a biaryl linkage between two aromatic amino acids. Recent genomic analyses revealed that the minimal biosynthetic prerequisite of biarylitide biosynthesis consists of only one ribosomally synthesized pentapeptide precursor as the substrate and a modifying cytochrome-P450-dependent enzyme. In silico analyses revealed that minimal biarylitide RiPP clusters are widespread among natural product producers across phylogenetic borders, including myxobacteria. We report here the genome-guided discovery of the first myxobacterial biarylitide MeYLH, termed Myxarylin, from Pyxidicoccus fallax An d48. Myxarylin was found to be an N-methylated tripeptide that surprisingly exhibits a C–N biaryl crosslink. In contrast to Myxarylin, previously isolated biarylitides are N-acetylated tripeptides that feature a C–C biaryl crosslink. Furthermore, the formation of Myxarylin was confirmed by the heterologous expression of the identified biosynthetic genes in Myxococcus xanthus DK1622. These findings expand the structural and biosynthetic scope of biarylitide-type RiPPs and emphasize the distinct biochemistry found in the myxobacterial realm.

Highlights

Myxobacteria are a phylum of Gram-negative bacteria that display a variety of unusual “behavioral” traits, such as coordinated swarming and the formation of macroscopic, multicellular fruiting bodies [1,2]
CA032A, the myxobacterial strain Pyxidicoccus fallax An d48—a strain that has already been shown to be a prolific producer of bacterial secondary metabolites [25,26,27]—contains the biarylitide open reading frames (ORFs) bytA with the encoded peptide sequence MNYLH
We describe the discovery, isolation, full-structure elucidation and heterologous production of the first myxobacterial biarylitide with the sequence MeYLH called Myxarylin, which displays biaryl crosslinking distinct from previously described members of the biarylitide family

Summary

Introduction

Myxobacteria are a phylum of Gram-negative bacteria that display a variety of unusual “behavioral” traits, such as coordinated swarming and the formation of macroscopic, multicellular fruiting bodies [1,2]. In addition to their unique “social behavior”, myxobacteria are a viable source for a multitude of natural products, exhibiting diverse biological activities due to their biosynthetic gene cluster (BGC)-rich genomes [3]. In contrast to NRPS and PKS gene clusters, which encode large enzyme complexes containing catalytic domains with high sequence homology, other types of BGCs, such as ribosomally synthesized and post-translationally modified peptide (RiPP) BGCs, are more difficult to identify and annotate as they are usually encoded by small, oftentimes poorly conserved open reading frames (ORFs) [7]

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Results

Conclusion