bw [Search on AGR]
Drosophila melanogaster brown (bw) encodes a member of the traffic ATPase (or ABC) family of membrane transporters. It is believed to heterodimerize with the product of w. bw and w are necessary to import guanine, a precursor for the red pteridine pigments, into pigment cells of the eyes, Malpighian tubules and testis sheath.