Post-Translational Tyrosine Geranylation in Cyanobactin Biosynthesis

Abstract

Prenylation is a widespread modification widely that improves the biological activities of secondary metabolites. This reaction also represents a key modification step in biosyntheses of cyanobactins, a family of ribosomally synthesized and posttranslationally modified peptides (RiPPs) produced by cyanobacteria. In cyanobactins, amino acids are commonly isoprenylated by ABBA prenyltransferases that use C5 donors. A potential exception was the discovery of piricyclamides, from a fresh-water cyanobacterium were proposed to have a C10 geranyl group. Here we characterize a novel geranyltransferase involved in piricyclamide biosynthesis. Using the purified enzyme, we show that the enzyme PirF catalyzes Tyr O-geranylation, which is an unprecedented posttranslational modification. In addition, the combination of enzymology and analytical chemistry revealed the structure of the final natural product, piricyclamide 7005E1, and the regioselectivity of PirF, which has potential as a synthetic biological tool providing drug-like properties to diverse small molecules.

Mechanisms and Evolution of Diversity-Generating RiPP Biosynthesis

“…Furthermore, after the installation of azoles and head-to-tail cyclization, cyanobactins are further diversified in tailoring reactions, as is found for many natural product classes [4,5] but thus far not for prochlorosins. These tailoring modifications include prenylation of side chains and modification of the N and C termini [37,[99][100][101][102][103][104][105]. Evidence for a kinetic trade-off that allows the high substrate tolerance of these tailoring enzymes has been reported [106], suggesting that they are generalist enzymes.…”

A Single Amino Acid Switch Alters the Isoprene Donor Specificity in Ribosomally Synthesized and Post-Translationally Modified Peptide Prenyltransferases

“…Subsequent structural characterization of piricyclamide 7005E1 demonstrated that the final product is a cyclic peptide (cyc-MSGVDYYNP) that is O -geranylated on Tyr, and in vitro reconstitution demonstrated that PirF is a geranyltransferase that can modify the hydroxyl oxygen of Tyr in peptide substrates. 16…”

Biocatalysis for terpene-based polymers

“…With respect to product diversity, prenylation of nonterpene-derived motifs in meroterpenoids is abundant in nature [46]. Halogenation by vanadium haloperoxidases [47] generate cyclic and halogenated (mero)terpenoids [48], shown here for the napyradiomycin family of natural products (15).…”