Identification of a retinal protein in Drosophila with antibody to the α subunit of bovine brain G o protein

An antibody directed against the α o subunit of bovine brain G o (R4) was used to identify a Drosophila retinal protein which may be the analogue of vertebrate transducin. The immunoreactivity appears predominantly in the retinal and occellar rhabdomeres. On a Western blot, the antibody recognizes a 41 kDa protein that is present in the heads of yellow white flies, but not in the heads of eyeless mutant flies, eyes absent. This protein is not recognized by an antibody raised against Drosophila α o . Antibody R4 intensely stains rhabdomeres and, to a lesser extent, the neuropil of the central nervous system in tissue sections of adult flies. Antibody to Drosophila α o stains the neuropil of the central nervous system, but does not stain rhabdomeres. In developing flies, faint immunoreactivity appears in the retinal rhabdomeres at about 70% of the time through pupal development and increases to its apparent adult maximal level about 1 day after eclosion. Tissue sections from a phototransduction mutant, norp A , have retinal immunoreactivity at normal levels up to about 1 week after eclosion, but by 2 weeks, immunoreactivity has largely disappeared. This disappearance parallels the degeneration of the retina in norp A mutants. In Drosophila and other invertebrates, light activates a phospholipase C in the retina. The identification of a protein in Drosophila rhabdomeres with an antibody raised against a mammalian G protein α subunit thought to be involved in phospholipase C activation suggests that there may be common structural features between the putative Drosophila transducin and α 0 , The identification of regions common to mammalian α 0 and Drosophila transducin may then provide clues to the structural requirements for PLC activation.