6DXA image
Entry Detail
PDB ID:
6DXA
Keywords:
Title:
Crystal structure of chalcone synthase from Pinus sylvestris
Biological Source:
Source Organism:
PDB Version:
Deposition Date:
2018-06-28
Release Date:
2018-10-17
Method Details:
Experimental Method:
Resolution:
2.01 Å
R-Value Free:
0.21
R-Value Work:
0.15
R-Value Observed:
0.16
Space Group:
P 1 21 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Chalcone synthase
Chain IDs:A, B
Chain Length:396
Number of Molecules:2
Biological Source:Pinus sylvestris
Modified Residue
Compound ID Chain ID Parent Comp ID Details 2D Image
CSD A CYS modified residue
Primary Citation
Mechanistic basis for the evolution of chalcone synthase catalytic cysteine reactivity in land plants.
J. Biol. Chem. 293 18601 18612 (2018)
PMID: 30291143 DOI: 10.1074/jbc.RA118.005695

Abstact

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.

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