1Z8N

Crystal structure of Arabidopsis thaliana Acetohydroxyacid synthase In Complex With An Imidazolinone Herbicide, Imazaquin

Summary for 1Z8N

• Entry DOI: 10.2210/pdb1z8n/pdb
• Related: 1JSC 1N0H 1T9B 1YBH 1YHZ 1YI0
• Descriptor: Acetolactate synthase, MAGNESIUM ION, 2-(4-ISOPROPYL-4-METHYL-5-OXO-4,5-DIHYDRO-1H-IMIDAZOL-2-YL)QUINOLINE-3-CARBOXYLIC ACID, ... (7 entities in total)
• Functional Keywords: acetohydroxyacid synthase, acetolactate synthase, herbicide, imidazolinone, thiamin diphosphate, fad, inhibitor, cysteine-s-dioxide, ches, transferase
• Biological source: Arabidopsis thaliana (thale cress)
• Cellular location: Plastid, chloroplast: P17597
• Total number of polymer chains: 1
• Total formula weight: 66656.79

Authors

McCourt, J.A.,Pang, S.S.,King-Scott, J.,Guddat, L.W.,Duggleby, R.G. (deposition date: 2005-03-31, release date: 2006-01-17, Last modification date: 2024-11-06)

Primary citation

McCourt, J.A.,Pang, S.S.,King-Scott, J.,Guddat, L.W.,Duggleby, R.G.
Herbicide-binding sites revealed in the structure of plant acetohydroxyacid synthase
Proc.Natl.Acad.Sci.Usa, 103:569-573, 2006

PubMed Abstract: The sulfonylureas and imidazolinones are potent commercial herbicide families. They are among the most popular choices for farmers worldwide, because they are nontoxic to animals and highly selective. These herbicides inhibit branched-chain amino acid biosynthesis in plants by targeting acetohydroxyacid synthase (AHAS, EC 2.2.1.6). This report describes the 3D structure of Arabidopsis thaliana AHAS in complex with five sulfonylureas (to 2.5 A resolution) and with the imidazolinone, imazaquin (IQ; 2.8 A). Neither class of molecule has a structure that mimics the substrates for the enzyme, but both inhibit by blocking a channel through which access to the active site is gained. The sulfonylureas approach within 5 A of the catalytic center, which is the C2 atom of the cofactor thiamin diphosphate, whereas IQ is at least 7 A from this atom. Ten of the amino acid residues that bind the sulfonylureas also bind IQ. Six additional residues interact only with the sulfonylureas, whereas there are two residues that bind IQ but not the sulfonylureas. Thus, the two classes of inhibitor occupy partially overlapping sites but adopt different modes of binding. The increasing emergence of resistant weeds due to the appearance of mutations that interfere with the inhibition of AHAS is now a worldwide problem. The structures described here provide a rational molecular basis for understanding these mutations, thus allowing more sophisticated AHAS inhibitors to be developed. There is no previously described structure for any plant protein in complex with a commercial herbicide.

PubMed: 16407096
DOI: 10.1073/pnas.0508701103

Experimental method

X-RAY DIFFRACTION (2.8 Å)