A Drosophila melanogaster G protein alpha subunit gene is expressed primarily in embryos and pupae

A G protein alpha subunit gene has been isolated from a Drosophila melanogaster genomic library using a combination of bovine rod and cone transducin alpha subunit cDNAs as a probe under reduced stringency conditions. The gene, DG alpha 1, encodes a protein with an amino acid sequence 78% identical to bovine Gi alpha 1. However, unlike all reported Gi alpha subunit the DG alpha 1-encoded protein is not expected to be a pertussis toxin substrate, because it lacks a cysteine at the appropriate site. The protein coding region of the gene is split by four introns. The sequence of a head tissue cDNA clone, as well as amino acid similarities to mammalian G proteins, confirms this exon/intron structure. Northern blots of total cellular RNA reveal a major 2.3-kilobase transcript and a less abundant 1.7-kilobase transcript. These transcripts are most abundant in RNA from embryos and pupae. The DG alpha 1 gene is located on band 65C on the left arm of the third chromosome, on the basis of in situ hybridizations to Drosophila salivary gland polytene chromosomes.