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

DOI: 10.1038/s41598-020-71850-w DOI Help

Authors: Asha V. Nair (University of Bristol) , Alice Robson (University of Bristol) , Thomas D. Ackrill (University of Bristol) , Marisa Till (University of Bristol) , Matthew J. Byrne (University of Bristol) , Catherine R. Back (University of Bristol) , Kavita Tiwari (University of Bristol) , Jonathan A. Davies (University of Bristol) , Christine L. Willis (University of Bristol) , Paul R. Race (University of Bristol)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Scientific Reports , VOL 10

State: Published (Approved)
Published: September 2020
Diamond Proposal Number(s): 17212

Open Access Open Access

Abstract: 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.

Journal Keywords: Biocatalysis; Biosynthesis

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: I04-Macromolecular Crystallography

Documents:
s41598-020-71850-w.pdf

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