ATP-dependent transporter of the ATP-binding cassette (ABC) family which transports various molecules including bioamines, neurotransmitters and metabolic intermediates (By similarity). In the eye and probably in association with w/white, required for the transport of the eye red pigment precursor, guanine, into pigment cell granules (PubMed:7635284). In Malpighian tubules, involved in guanine uptake (By similarity). Probably in association with w/white, involved in aging-induced intestinal stem cell proliferation in the midgut by regulating tetrahydrofolate transport (By similarity). ATP + guanine(out) + H2O = ADP + guanine(in) + H(+) + phosphate ATP + H2O + riboflavin(in) = ADP + H(+) + phosphate + riboflavin(out) (6S)-5,6,7,8-tetrahydrofolate(out) + ATP + H2O = (6S)-5,6,7,8-tetrahydrofolate(in) + ADP + H(+) + phosphate May form a heterodimer with w/white. Expressed in eyes. Belongs to the ABC transporter superfamily. ABCG family. Eye pigment precursor importer (TC 3.A.1.204) subfamily.