A G-PROTEIN BETA-SUBUNIT IS ESSENTIAL FOR DICTYOSTELIUM DEVELOPMENT

Recent studies have demonstrated that G-protein-linked signal transduc tion pathways play a significant role in the developmental program of the simple eukaryotic organism Dictyostelium. We have reported previou sly the isolation of a G-protein beta-subunit and present here a more complete analysis of this gene. Low-stringency Southern blots and RFLP mapping studies suggest that the beta-subunit is a unique gene found on linkage group II. Its deduced amino acid sequence of 347 residues i s approximately 60% identical to those of the human, Drosophila, and C aenorhabditis elegans beta-subunits. The carboxy-terminal 300 residues are about 70% identical; the amino-terminal 50 residues are quite div ergent, containing only 10 identities. At all stages of growth and dev elopment, a single 1.9-kb beta-subunit mRNA is present at a high level , and a specific antibody detects a single 37-kD protein. We propose t hat G-protein heterotrimers are formed when this beta-subunit couples with each of the eight distinct G-protein alpha-subunits that are tran siently expressed during development. Targeted disruption of the beta- subunit gene had no effect on the viability of haploid cells, but resu lted in the inability of cells to aggregate.