title: Specific binding of a dichloroacetamide herbicide safener in maize at a site that also binds thiocarbamate and chloroacetanilide herbicides.
abstract: Dichloroacetamide safeners such as N,N-diallyl-2,2-dichloroacetamide and (R,S)-3-dichloroacetyl-2,2,5-trimethyl-1,3-oxazolidine protect maize (Zea mays) against injury from thiocarbamate and chloroacetanilide herbicides. Binding activity of tritium-labeled (R,S)-3-dichloroacetyl-2,2,5-trimethyl-1,3-oxazolidine (15 Ci/mmol; referred to as [3H]Saf) was characterized in extracts of etiolated maize seedlings. The binding is saturable, involves a single class of binding sites (Kd 0.12 microM; maximal binding in coleoptiles 0.53 nmol/g fresh weight, equivalent to 55 pmol/mg protein), and is sensitive to boiling and protease treatment. Binding in etiolated maize seedlings is highest in the coleoptile and lowest in the leaves. Binding of [3H]Saf also occurs in etiolated sorghum (Sorghum bicolor) shoots but not several other cereals. There is a good correlation between known safener effectiveness and the concentration that inhibits [3H]Saf binding half-maximally among 21 dichloroacetamides and related compounds. N,N-Diallyl-2,2-dichloroacetamide had the lowest inhibitor concentration that reduces specific binding by 50% (IC50), 0.01 microM. [3H]Saf binding is inhibited by 4 chloroacetanilide herbicides with IC50 values of 0.07 to 0.48 microM and by 12 thiocarbamate herbicides and analogs with IC50 values of 0.06 to 2.3 microM. The inhibition of [3H]Saf binding by alachlor and S-ethyl dipropylthiocarbamate is competitive.
mesh_terms: D000081:Acetamides / Q000378:metabolism; D001665:Binding Sites; D002219:Carbamates; D006540:Herbicides / Q000037:antagonists & inhibitors* / Q000378:metabolism* / Q000633:toxicity; D007700:Kinetics; D010080:Oxazoles / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D011485:Protein Binding; D003313:Zea mays / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D000081:Acetamides; D002219:Carbamates; D006540:Herbicides; D010080:Oxazoles; D010940:Plant Proteins; C092143:3-(dichloroacetyl)-2,2,5-trimethyl-1,3-oxazolidine; C032619:2,2-dichloroacetamide