Immunolocalization of retinal-binding protein (RALBP)-like protein in compound eye and ocellus of drosophila melanogaster (Diptera : Drosophilidae)

A retinal-binding protein (RALBP)-like protein was found in Drosophila melanogaster (Diptera: Drosophilidae) visual system by immunoelectron microscopy using anti-squid RALBP antibody. Immunoblot analysis showed that RALBP-like protein has a molecular weight of about 120 kDa. It was detected mainly in the central cavity of compound eye ommatidia and in the interphotoreceptor space of the ocellus. The protein was localized in the cytoplasm of photoreceptor cells as well. However, these molecules were not detected in the cone cells, crystalline cone, and pigment cells. The molecular size and the localization of the Drosophila RALBP-like protein are similar to those of the vertebrate interphotoreceptor retinoid binding protein (IRBP). It is suggested that this protein may function as a Drosophila IRBP.