title: Regulatory interactions in Arabidopsis thaliana acetohydroxyacid synthase.
abstract: Acetohydroxyacid synthase (AHAS; EC 4.1.3.18) contains catalytic and regulatory subunits, the latter being required for sensitivity to feedback regulation by leucine, valine and isoleucine. The regulatory subunit of Arabidopsis thaliana AHAS possesses a sequence repeat and we have suggested previously that one repeat binds leucine while the second binds valine or isoleucine, with synergy between the two sites. We have mutated four residues in each repeat, based on a model of the regulatory subunit. The data confirm that there are separate leucine and valine/isoleucine sites, and suggest a complex pathway for regulatory signal transmission to the catalytic subunit.
authors.affiliation: Centre for Protein Structure, Function and Engineering, Department of Biochemistry and Molecular Biology, University of Queensland, 4072, Brisbane, Qld., Australia.
authors.forename: Yu Ting
authors.initials: YT
authors.lastname: Lee
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Duggleby
mesh_terms: D000095:Acetolactate Synthase / Q000235:genetics / Q000378:metabolism*; D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D001665:Binding Sites / Q000235:genetics; D007532:Isoleucine / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics; D014633:Valine / Q000378:metabolism
chemical_list: D007532:Isoleucine; D000095:Acetolactate Synthase; D007930:Leucine; D014633:Valine