Two forms of Drosophila melanogaster Gs alpha are produced by alternate splicing involving an unusual splice site.

Abstract

G proteins are responsible for modulating the activity of intracellular effector systems in response to receptor activation. The stimulatory G protein Gs is responsible for activation of adenylate cyclase in response to a variety of hormonal signals. In this report, we describe the structure of the gene for the alpha subunit of Drosophila melanogaster Gs. The gene is approximately 4.5 kilobases long and is divided into nine exons. The exon-intron structure of the Drosophila gene shows substantial similarity to that of the human gene for Gs alpha. Alternate splicing of intron 7, involving either use of an unusual TG or consensus AG 3' splice site, results in transcripts which code for either a long (DGs alpha L) or short (DGs alpha S) form of Gs alpha. These subunits differ by inclusion or deletion of three amino acids and substitution of a Ser for a Gly. The two forms of Drosophila Gs alpha differ in a region where no variation in the primary sequence of vertebrate Gs alpha subunits has been observed. In vitro translation experiments demonstrated that the Drosophila subunits migrate anomalously on sodium dodecyl sulfate-polyacrylamide gels with apparent molecular weights of 51,000 and 48,000. Additional Gs alpha transcript heterogeneity reflects the use of multiple polyadenylation sites.