Present address: Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA.
Systematic characterization of mutations in yeast acetohydroxyacid synthase
Interpretation of herbicide-resistance data
Article first published online: 12 JUN 2003
European Journal of Biochemistry
Volume 270, Issue 13, pages 2895–2904, July 2003
How to Cite
Duggleby, R. G., Pang, S. S., Yu, H. and Guddat, L. W. (2003), Systematic characterization of mutations in yeast acetohydroxyacid synthase. European Journal of Biochemistry, 270: 2895–2904. doi: 10.1046/j.1432-1033.2003.03671.x
Enzymes: acetohydroxyacid synthase (EC 22.214.171.124); ketol-acid reductoisomerase (EC 126.96.36.199); dihydroxy-acid dehydratase (EC 188.8.131.52); branched-chain amino acid transaminase (EC 184.108.40.206); isopropylmalate synthase (EC 220.127.116.11); isopropylmalate isomerase (EC 18.104.22.168); isopropylmalate dehydrogenase (EC 22.214.171.124).
Note: a web site is available at http://smms.uq.edu.au/duggleby
- Issue published online: 12 JUN 2003
- Article first published online: 12 JUN 2003
- (Received 17 March 2003, revised 21 April 2003, accepted 15 May 2003)
- acetohydroxyacid synthase;
- herbicide inhibition;
- herbicide-resistance mutations;
Acetohydroxyacid synthase (AHAS, EC 126.96.36.199) catalyses the first step in branched-chain amino acid biosynthesis and is the target for sulfonylurea and imidazolinone herbicides, which act as potent and specific inhibitors. Mutants of the enzyme have been identified that are resistant to particular herbicides. However, the selectivity of these mutants towards various sulfonylureas and imidazolinones has not been determined systematically. Now that the structure of the yeast enzyme is known, both in the absence and presence of a bound herbicide, a detailed understanding of the molecular interactions between the enzyme and its inhibitors becomes possible. Here we construct 10 active mutants of yeast AHAS, purify the enzymes and determine their sensitivity to six sulfonylureas and three imidazolinones. An additional three active mutants were constructed with a view to increasing imidazolinone sensitivity. These three variants were purified and tested for their sensitivity to the imidazolinones only. Substantial differences are observed in the sensitivity of the 13 mutants to the various inhibitors and these differences are interpreted in terms of the structure of the herbicide-binding site on the enzyme.