J Biol Chem, Vol. 274, Issue 53, 37605-37610, December 31, 1999

A Novel G Isolated from Drosophila Constitutes a Visual G Protein  Subunit of the Fly Compound Eye^*

Simone Schulz, Armin Huber, Karin Schwab, and Reinhard Paulsen

From the Department of Cell and Neurobiology, Institute of Zoology, University of Karlsruhe, 76128 Karlsruhe, Germany

Visual transduction in the compound eye of flies is a well established model system for the study of G protein-coupled transduction pathways. To characterize key components of the phototransduction cascade we performed substractive hybridization screening. We cloned the cDNA coding for the visual G (G_e) subunit from Drosophila which had so far eluded identification at the molecular level. Northern blot analysis revealed the presence of a major, 1.4-kilobase(kb) G_e transcript and two minor transcripts of 1.8 and 6 kb in size. The major 1.4-kb mRNA is expressed preferentially in the eye. The spatial expression pattern determined for G_e as well as co-immunoprecipitation experiments demonstrated that G_e dimerizes with G_e to form the heterodimeric G subunit which functions in visual transduction in the Drosophila compound eye. G_e shares common characteristics with the visual G subunits of human rod and cone photoreceptors although different classes of G subunits are employed in vertebrate and invertebrate phototransduction. By the molecular cloning and characterization of the visual  subunit of Drosophila one of the few missing links in the well studied Drosophila phototransduction cascade has been characterized to complete our knowledge about the Drosophila visual transduction pathway.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank^TM/EMBL Data Bank with accession number(s) AJ 250440 (DmG_e) and AJ 250441 (CvG_e).