Acetyl-coenzyme A carboxylase (ACCase) has been identified as one of the most important targets of herbicides. In the present study, we constructed homology models of the carboxyl-transferase (CT) domain of ACCase from sensitive and resistant foxtail and used these models as templates to study the molecular mechanism of herbicide resistance and stereochemistry-activity relationships of aryloxyphenoxypropionates (APPs). In the homology modeling structures, the dimer of the CT domain was formed by the side-to-side arrangement of the two monomers, in such a way that the N domain of one molecule i...