This family represents a conserved pair of two transmembrane alpha-helices. All members carry the two pairs of TMs. BTP is a form of drug efflux pump, that actively tranports chlorhexidine out of the cell. Chlorhexidine, a bisbiguanide antimicrobial agent, is commonly used as an antiseptic and disinfectant in hospitals, and there is an increasing problem with resistance to it in some pathogenic bacteria. BTP is localized in the cytoplasmic membrane.