Differentiating 5-thiooxazoles from oxazolone-coupled thioamides in RiPP natural products

Authors

Manley, O. M., Shriver, T. J., Ayala, J. M., Owen, B. C., Ziarek, J. J., Rosenzweig, A. C.

Abstract

Conversion of cysteine residues to 5-thiooxazole moieties by multinuclear nonheme iron-dependent oxidative enzymes (MNIOs) is a prevalent modification in ribosomally synthesized, post-translationally modified peptide (RiPP) natural products. However, this post-translational modification (PTM) is difficult to distinguish from MNIO-produced oxazolone-coupled thioamides, such as those present in the RiPP methanobactin. The RiPP virulence factor oxazolin contains six copper-binding heterocycles installed by an MNIO. Here, we reassign these PTMs, originally described as oxazolones/thioamides, as 5-thiooxazoles on the basis of detailed comparative chemical and structural characterization of oxazolin and methanobactin. These data establish a benchmark for differentiating these two PTMs in newly discovered RiPPs.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 11 Jun 2026.

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