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Structure and mechanism of a dehydratase/decarboxylase enzyme couple involved in polyketide β-methyl branch incorporation

Lookup NU author(s): Professor Paul RaceORCiD

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Abstract

© 2020, The Author(s). Complex polyketides of bacterial origin are biosynthesised by giant assembly-line like megaenzymes of the type 1 modular polyketide synthase (PKS) class. The trans-AT family of modular PKSs, whose biosynthetic frameworks diverge significantly from those of the archetypal cis-AT type systems represent a new paradigm in natural product enzymology. One of the most distinctive enzymatic features common to trans-AT PKSs is their ability to introduce methyl groups at positions β to the thiol ester in the growing polyketide chain. This activity is achieved through the action of a five protein HCS cassette, comprising a ketosynthase, a 3-hydroxy-3-methylglutaryl-CoA synthase, a dehydratase, a decarboxylase and a dedicated acyl carrier protein. Here we report a molecular level description, achieved using a combination of X-ray crystallography, in vitro enzyme assays and site-directed mutagenesis, of the bacillaene synthase dehydratase/decarboxylase enzyme couple PksH/PksI, responsible for the final two steps in β-methyl branch installation in this trans-AT PKS. Our work provides detailed mechanistic insight into this biosynthetic peculiarity and establishes a molecular framework for HCS cassette enzyme exploitation and manipulation, which has future potential value in guiding efforts in the targeted synthesis of functionally optimised ‘non-natural’ natural products.

Publication metadata

Author(s): Nair AV, Robson A, Ackrill TD, Till M, Byrne MJ, Back CR, Tiwari K, Davies JA, Willis CL, Race PR

Publication type: Article

Publication status: Published

Journal: Scientific Reports

Year: 2020

Volume: 10

Issue: 1

Online publication date: 18/09/2020

Acceptance date: 30/07/2020

ISSN (electronic): 2045-2322

Publisher: Nature Research

URL: https://doi.org/10.1038/s41598-020-71850-w

DOI: 10.1038/s41598-020-71850-w

PubMed id: 32948786

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