Amino acid residues conferring herbicide resistance in tobacco acetohydroxy acid synthase.

ABSTRACT: The enzyme AHAS (acetohydroxy acid synthase), which is involved in the biosynthesis of valine, leucine and isoleucine, is the target of several classes of herbicides. A model of tobacco AHAS was generated based on the X-ray structure of yeast AHAS. Well conserved residues at the herbicide-binding site were identified, and the roles of three of these residues (Phe-205, Val-570 and Phe-577) were determined by site-directed mutagenesis. The Phe-205 mutants F205A, F205H, F205W and F205Y showed markedly decreased levels of catalytic efficiency, and cross-resistance to two or three classes of herbicides, i.e. Londax (a sulphonylurea herbicide), Cadre (an imidazolinone herbicide) and TP (a triazolopyrimidine derivative). None of the mutations caused significant changes in the secondary or tertiar

SUBMITTER: Jung SM 

PROVIDER: S-EPMC1134043 | biostudies-literature | 2004 Oct

REPOSITORIES: biostudies-literature