Reassignment of the Structure of a Tryptophan-Containing Cyclic Tripeptide Produced by the Biarylitide Crosslinking Cytochrome P450.

The structure of the sidechain crosslinked Tyr-Leu-Trp peptide produced by the biarylitide crosslinking cytochrome P450 from Micromonospora sp. MW-13 has been reanalysed by a series of NMR, computational and isotope labelling experiments and shown to contain a C-N rather than a C-O bond. Additional in vivo experiments using such a modified peptide show there is a general tolerance of biarylitide crosslinking P450 enzymes for histidine to tryptophan mutations within their minimal peptide substrate sequences despite the lack of such residues noted in natural biarylitide gene clusters. This work further highlights the impressive ability of P450s from biarylitide biosynthesis pathways to act as biocatalysts for the formation of a range of sidechain crosslinked tripeptides.