Mechanistic basis for the evolution of chalcone synthase catalytic cysteine reactivity in land plants
Name
Mechanistic basis for the evolution of chalcone synthase catalytic cysteine reactivity in land plants_proof.pdf
Description
Accepted version
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4.73 MB
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Author(s)
Liou, Geoffrey
Chiang, Ying-Chih
Wang, Yi
Weng, Jing-Ke
Date Issued
October 2018
Journal
Journal of Biological Chemistry
Publisher
American Society for Biochemistry & Molecular Biology (ASBMB)
Citation
Liou, Geoffrey et al. "Mechanistic basis for the evolution of chalcone synthase catalytic cysteine reactivity in land plants." Journal of Biological Chemistry 293, 48 (November 2018): 18601-18612 © 2018 Liou et al
Version
Author's final manuscript
Abstract
Flavonoids are important polyphenolic natural products, ubiquitous in land plants, that play diverse functions in plants’ survival in their ecological niches, including UV protection, pigmentation for attracting pollinators, symbiotic nitrogen fixation, and defense against herbivores. Chalcone synthase (CHS) catalyzes the first committed step in plant flavonoid biosynthesis and is highly conserved in all land plants. In several previously reported crystal structures of CHSs from flowering plants, the catalytic cysteine is oxidized to sulfinic acid, indicating enhanced nucleophilicity in this residue associated with its increased susceptibility to oxidation. In this study, we report a set of new crystal structures of CHSs representing all five major lineages of land plants (bryophytes, lycophytes, monilophytes, gymnosperms, and angiosperms), spanning 500 million years of evolution. We reveal that the structures of CHS from a lycophyte and a moss species preserve the catalytic cysteine in a reduced state, in contrast to the cysteine sulfinic acid seen in all euphyllophyte CHS structures. In vivo complementation, in vitro biochemical and mutagenesis analyses, and molecular dynamics simulations identified a set of residues that differ between basal-plant and euphyllophyte CHSs and modulate catalytic cysteine reactivity. We propose that the CHS active-site environment has evolved in euphyllophytes to further enhance the nucleophilicity of the catalytic cysteine since the divergence of euphyllophytes from other vascular plant lineages 400 million years ago. These changes in CHS could have contributed to the diversification of flavonoid biosynthesis in euphyllophytes, which in turn contributed to their dominance in terrestrial ecosystems.
MIT Department
Massachusetts Institute of Technology. Department of Biology
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DOI of Published Version
https://doi.org/10.1074/jbc.ra118.005695
