Energy-dependent efflux transporter responsible for decreased drug accumulation in multidrug-resistant cells (By similarity). Specifically present in limbal stem cells, where it plays a key role in corneal development and repair (PubMed:25030174). ATP + daunorubicin(in) + H2O = ADP + daunorubicin(out) + H(+) + phosphate In developing eye, expressed in basal limbal epithelium but not in central cornea. Acts as a marker of limbal stem cells. Defects in corneal development. While eyes contain all anterior and posterior segment components, corneas show developmental abnormalities characterized by decreased cellularity of the apical epithelial layer and disorganized basal and wing cell layers. Defects are due to depletion of quiescent limbal stem cells, leading to enhanced proliferation and apoptosis, and resulting in defective corneal differentiation and wound healing. Belongs to the ABC transporter superfamily. ABCB family. Multidrug resistance exporter (TC 3.A.1.201) subfamily.