ATP-dependent transporter of the ATP-binding cassette (ABC) family which transports various molecules including bioamines, neurotransmitters, metabolic intermediates and second messengers (PubMed:812484, PubMed:117796, PubMed:6788034, PubMed:10407069, PubMed:18310115, PubMed:18931318, PubMed:33820991). In the eye, required for the transport of the eye red and brown pigment precursors, guanine and tryptophan, into pigment cell granules (PubMed:10407069, PubMed:8144619). Probably in association with bw/brown, involved in the transport of guanine (PubMed:117796). Probably in association with st/scarlet involved in the transport of kynurenine and probably tryptophan (PubMed:812484). Involved in the transport of kynurenine in pupal eyes (PubMed:812484). May play a role in histamine uptake by the lamina epithelial glia which surrounds photoreceptors R1-R6 (PubMed:18931318). In Malpighian tubules, involved in the transport of cGMP, guanine, xanthine, riboflavin, kynurenine and tryptophan (PubMed:812484, PubMed:117796, PubMed:6788034, PubMed:18310115). Probably in association with br/brown, involved in aging-induced intestinal stem cell proliferation in the midgut by regulating tetrahydrofolate transport (PubMed:33820991). Probably in association with st/scarlet, plays a role in zinc storage granule biogenesis in Malpighian tubule principal epithelial cells (PubMed:29367274). 3',5'-cyclic GMP(in) + ATP + H2O = 3',5'-cyclic GMP(out) + ADP + H(+) + phosphate 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 ATP + H2O + L-tryptophan(out) = ADP + H(+) + L-tryptophan(in) + phosphate ATP + H2O + L-kynurenine(out) = ADP + H(+) + L-kynurenine(in) + phosphate ATP + H2O + xanthine(out) = ADP + H(+) + phosphate + xanthine(in) May form a heterodimer with bw/brown (Probable). May form a heterodimer with st/scarlet (Probable). Co-localizes with st/scarlet to pigment granules within pigment cells and retinula cells of the compound eye. Expressed in the head (at protein level) (PubMed:11294610). Expressed in the eye, specifically in retina primary pigment cells, in the basement membrane of the base of secondary and tertiary pigment cells, and in retinula cells (at protein level) (PubMed:18931318, PubMed:11294610). Expressed in the retina underlying lamina in the epithelial glia that surrounds the array of lamina cartridges (at protein level) (PubMed:18931318). Weakly expressed in photoreceptors, specifically in terminals of R1-R6, R7 and R8 (at protein level) (PubMed:18931318). Expressed at very low levels in medulla and central brain (at protein level) (PubMed:18931318). Expressed in principal cells of the Malpighian tubules (PubMed:33820991). Up-regulated during aging in intestinal stem cells. Eyes are white due to a defect in color pigment production (PubMed:18310115, PubMed:33820991). Malpighian tubules appear clear or white (PubMed:18310115, PubMed:29367274). Loss of st/scarlet protein in the pigment cells and retinula cells of the compound eye (PubMed:11294610). Transport of cGMP, but not cAMP, is inhibited in Malpighian tubules; however, basal fluid transport rates or rates stimulated by cGMP in the tubules are normal (PubMed:18310115). In Malpighian tubules, uptake of guanine, xanthine and riboflavin is impaired while uptake of hypoxanthine, guanosine and adenine is not affected (PubMed:117796). In Malpighian tubules, kynurenine and tryptophan uptake is impaired; however, incorporation of tryptophan into proteins is not affected (PubMed:6788034, PubMed:812484). In pupal eyes, kynurenine uptake is impaired (PubMed:812484). In the head, 50% reduction in histamine levels, 60% reduction in dopamine levels and 32% reduction in serotonin (5-HT) levels (PubMed:18931318). Specifically, histamine levels are reduced in the retina, the retina lamina and the central brain (PubMed:18931318). In addition, in lamina photoreceptor terminals R1-R6, numbers of synaptic vesicles and capitate projections, which are sites of endocytosis of vesicle membrane, are reduced (PubMed:18931318). In young and old flies, reduces the levels of several metabolites, including tryptophan, kynurenine, kynurenic acid, 3-hydroxykynurenine, guanosine, xanthine, riboflavin and tetrahydrofolate, and increases the levels of guanine (PubMed:33820991). Inhibits aging-induced intestinal stem cell proliferation (PubMed:33820991). 3-fold reduction in Malpighian tubule zinc stores (PubMed:29367274). Severe reduction of copulation success and reduced courting activities in males (PubMed:28794482). RNAi-mediated knockdown in central nervous system causes a delay in locomotor recovery from anoxia with no effect on eye pigmentation (PubMed:27029736). RNAi-mediated knockdown in serotonergic neurons, causes a delay in locomotor recovery from anoxia (PubMed:27029736). Belongs to the ABC transporter superfamily. ABCG family. Eye pigment precursor importer (TC 3.A.1.204) subfamily.