Membrane potential-dependent conformational changes in mitochondrially bound hexokinase of brain

Previously characterized monoclonal antibodies (Mabs) were used in a study of Type I hexokinase from rat brain. Based on the relative reactivity of th ese Mabs with soluble and mitochondrially bound forms, binding to mitochond ria was shown to affect specific epitopic regions in both N- and C-terminal halves of the enzyme and to modulate conformational changes induced by bin ding of the ligands, Glc or ATP. Reactivities with Mabs recognizing epitope s in two defined regions of the N-terminal half and one defined region of t he C-terminal half of the mitochondrially bound enzyme were selectively aff ected by mitochondrial membrane potential, or by addition of oligomycin, ca rboxyatractyloside, or bongkrekic acid. The GIc-6-P analog, 1,5-anhydrogluc itol-6-P, was much more effective as a competitive inhibitor against extram itochondrial ATP than against intramitochondrial ATP generated by oxidative phosphorylation, These results provide further insight into the role of he xokinase-mitochondrial interactions in regulation of cerebral glucose metab olism. (C) 2000 Academic Press.