4DOI

Crystal structure of Arabidopsis thaliana chalcone isomerase At3g55120 (AtCHI)

Summary for 4DOI

• Entry DOI: 10.2210/pdb4doi/pdb
• Related: 4DOK 4DOL 4DOO
• Descriptor: Chalcone--flavonone isomerase 1, NITRATE ION (3 entities in total)
• Functional Keywords: chalcone-flavanone isomerase, isomerase
• Biological source: Arabidopsis thaliana (mouse-ear cress,thale-cress)
• Total number of polymer chains: 2
• Total formula weight: 53495.12

Authors

Noel, J.P.,Louie, G.V.,Bowman, M.E. (deposition date: 2012-02-09, release date: 2012-05-09, Last modification date: 2023-09-13)

Primary citation

Ngaki, M.N.,Louie, G.V.,Philippe, R.N.,Manning, G.,Pojer, F.,Bowman, M.E.,Li, L.,Larsen, E.,Wurtele, E.S.,Noel, J.P.
Evolution of the chalcone-isomerase fold from fatty-acid binding to stereospecific catalysis.
Nature, 485:530-533, 2012

PubMed Abstract: Specialized metabolic enzymes biosynthesize chemicals of ecological importance, often sharing a pedigree with primary metabolic enzymes. However, the lineage of the enzyme chalcone isomerase (CHI) remained unknown. In vascular plants, CHI-catalysed conversion of chalcones to chiral (S)-flavanones is a committed step in the production of plant flavonoids, compounds that contribute to attraction, defence and development. CHI operates near the diffusion limit with stereospecific control. Although associated primarily with plants, the CHI fold occurs in several other eukaryotic lineages and in some bacteria. Here we report crystal structures, ligand-binding properties and in vivo functional characterization of a non-catalytic CHI-fold family from plants. Arabidopsis thaliana contains five actively transcribed genes encoding CHI-fold proteins, three of which additionally encode amino-terminal chloroplast-transit sequences. These three CHI-fold proteins localize to plastids, the site of de novo fatty-acid biosynthesis in plant cells. Furthermore, their expression profiles correlate with those of core fatty-acid biosynthetic enzymes, with maximal expression occurring in seeds and coinciding with increased fatty-acid storage in the developing embryo. In vitro, these proteins are fatty-acid-binding proteins (FAPs). FAP knockout A. thaliana plants show elevated α-linolenic acid levels and marked reproductive defects, including aberrant seed formation. Notably, the FAP discovery defines the adaptive evolution of a stereospecific and catalytically 'perfected' enzyme from a non-enzymatic ancestor over a defined period of plant evolution.

PubMed: 22622584
DOI: 10.1038/nature11009

Experimental method

X-RAY DIFFRACTION (1.55 Å)