Mutagenesis studies on the sensitivity of Escherichia coli acetohydroxyacid synthase II to herbicides and valine.
Acetohydroxyacid synthase (EC 4.1.3.18, also known as acetolactate synthase) isoenzyme II from Escherichia coli is inhibited by sulphonylurea and imidazolinone herbicides, although it is much less sensitive than the plant enzyme. This isoenzyme is also unusual in that it is not inhibited by valine. Mutating S100 (Ser(100) in one-letter amino acid notation) of the catalytic subunit to proline increases its sensitivity to sulphonylureas, but not to imidazolinones. Mutating P536 to serine, as found in the plant enzyme, had little effect on the properties of the enzyme. Mutating E14 of the regulatory subunit to glycine, either alone or in combination with the H29N (His(29)-->Asn) change, did not affect valine-sensitivity.
Lee
Y T
YT
Centre for Protein Structure, Function and Engineering, Department of Biochemistry, University of Queensland, Brisbane, Qld. 4072, Australia.
Duggleby
R G
RG
D000095:Acetolactate Synthase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D004926:Escherichia coli / Q000201:enzymology*; D006540:Herbicides / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D017386:Sequence Homology, Amino Acid; D014633:Valine / Q000494:pharmacology*
D006540:Herbicides; D000095:Acetolactate Synthase; D014633:Valine