 The exact mechanism(s) whereby ABCG5/ABCG8 exert their effects on sterol metabolism has not yet been clarified.But it is suggested that the ABCG5/ABCG8 heterodimer shuttles cholesterol from the inner leaflet of the canalicular membrane through a chamber formed by the two half-transporters.Following ATP binding and hydrolysis, the complex undergoes a conformational change, flipping a cholesterol molecule into the outer membrane leaflet in a configuration that favors its release into the canalicular space.