3R8W

Structure of 3-isopropylmalate dehydrogenase isoform 2 from Arabidopsis thaliana at 2.2 angstrom resolution

Summary for 3R8W

• Entry DOI: 10.2210/pdb3r8w/pdb
• Descriptor: 3-isopropylmalate dehydrogenase 2, chloroplastic, ACETATE ION (3 entities in total)
• Functional Keywords: dimer, isocitrate and isopropylmalate dehydrogenases family, leucine biosynthesis, glucosinolate biosynthesis, nadh, 3-isopropylmalate, chloroplast, oxidoreductase
• Biological source: Arabidopsis thaliana (mouse-ear cress,thale-cress)
• Cellular location: Plastid, chloroplast (By similarity): P93832
• Total number of polymer chains: 4
• Total formula weight: 174568.33

Authors

He, Y.,Galant, A.,Pang, Q.,Strul, J.M.,Balogun, S.,Jez, J.M.,Chen, S. (deposition date: 2011-03-24, release date: 2011-06-22, Last modification date: 2024-02-21)

Primary citation

He, Y.,Galant, A.,Pang, Q.,Strul, J.M.,Balogun, S.F.,Jez, J.M.,Chen, S.
Structural and functional evolution of isopropylmalate dehydrogenases in the leucine and glucosinolate pathways of Arabidopsis thaliana.
J.Biol.Chem., 286:28794-28801, 2011

PubMed Abstract: The methionine chain-elongation pathway is required for aliphatic glucosinolate biosynthesis in plants and evolved from leucine biosynthesis. In Arabidopsis thaliana, three 3-isopropylmalate dehydrogenases (AtIPMDHs) play key roles in methionine chain-elongation for the synthesis of aliphatic glucosinolates (e.g. AtIPMDH1) and leucine (e.g. AtIPMDH2 and AtIPMDH3). Here we elucidate the molecular basis underlying the metabolic specialization of these enzymes. The 2.25 Å resolution crystal structure of AtIPMDH2 was solved to provide the first detailed molecular architecture of a plant IPMDH. Modeling of 3-isopropylmalate binding in the AtIPMDH2 active site and sequence comparisons of prokaryotic and eukaryotic IPMDH suggest that substitution of one active site residue may lead to altered substrate specificity and metabolic function. Site-directed mutagenesis of Phe-137 to a leucine in AtIPMDH1 (AtIPMDH1-F137L) reduced activity toward 3-(2'-methylthio)ethylmalate by 200-fold, but enhanced catalytic efficiency with 3-isopropylmalate to levels observed with AtIPMDH2 and AtIPMDH3. Conversely, the AtIPMDH2-L134F and AtIPMDH3-L133F mutants enhanced catalytic efficiency with 3-(2'-methylthio)ethylmalate ∼100-fold and reduced activity for 3-isopropylmalate. Furthermore, the altered in vivo glucosinolate profile of an Arabidopsis ipmdh1 T-DNA knock-out mutant could be restored to wild-type levels by constructs expressing AtIPMDH1, AtIPMDH2-L134F, or AtIPMDH3-L133F, but not by AtIPMDH1-F137L. These results indicate that a single amino acid substitution results in functional divergence of IPMDH in planta to affect substrate specificity and contributes to the evolution of specialized glucosinolate biosynthesis from the ancestral leucine pathway.

PubMed: 21697089
DOI: 10.1074/jbc.M111.262519

Experimental method

X-RAY DIFFRACTION (2.25 Å)