Multiple alpha subunits of guanine nucleotide-binding proteins in Dictyostelium

Previous results have shown that chemotaxis and the expression of several classes of genes in Dictyostelium discoideum are regulated through a cell surface cAMP receptor interacting with guanine nucleotide-binding proteins (G proteins). We now describe cloning and sequencing of cDNAs encoding two G alpha protein subunits from Dictyostelium. The derived amino acid sequences show that they are 45% identical to each other and to G alpha protein subunits from mammals and yeast. Both cDNAs are complementary to multiple mRNAs that are differentially expressed during development. This evidence and analysis of mutants presented elsewhere suggest that they have distinct physiological functions.