Plant genome mining of burpitides from fused precursor peptides

Plants produce a large diversity of natural products while having some of the largest genomes found in nature. With increasing plant genomic resources, genome mining can uncover new natural product chemistry hidden in complex plant metabolomes guided by biosynthetic gene predictions. A growing class of plant natural products, for which genome mining is an effective discovery strategy, are a recently defined plant peptide class called burpitides. Burpitides are ribosomally synthesized and posttranslationally modified peptides (RiPP) which contain crosslinks between tryptophan or tyrosine and other amino acid side chains or the peptide backbone. These class-defining posttranslational modifications are formed by BURP-domain-containing proteins (named after their founding members) called burpitide cyclases. Burpitide cyclases can include the core peptide motif, i.e. the sequence of the final RiPP natural product, encoded in the same polypeptide as the BURP domain in so-called fused or autocatalytic burpitide cyclases. Therefore, fused burpitide cyclases enable prediction of candidate burpitide chemotypes from genome-derived BURP-domain gene sequences. Here, we outline a genome mining approach for fused burpitide cyclase products via bioinformatic structural prediction, peptide chemotyping, biosynthetic confirmation and structure elucidation.