Identification of Dictyostelium G_ɑ genes expressed during multicellular development

Abstract

Guanine nucleotide-binding protein (G protein)-mediated signal transduction constitutes a common mechanism by which cells receive and respond to a diverse set of environmental signals. Many of the signals involved in the developmental life cycle of the slime mold Dictyostelium have been postulated to be transduced by such pathways and, in some cases, these pathways have been demonstrated to be dependent on specific G proteins. Using the polymerase chain reaction, we have identified two additional Dictyostelium G_ɑ genes, G_ɑ4 and G_ɑ5, that are developmentally regulated. Transcripts from both of these genes are primarily expressed during the multicellular stages of development, suggesting possible roles in cell differentiation or morphogenesis. The entire G_ɑ 4 gene was sequenced and found to encode a protein consisting of 345 amino acids. The G_ɑ4 subunit is homologous to other previously identified G_ɑ subunits, including the Dictyostelium Gɑ1 (43% identity) and G_ɑ2 (41% identity) subunits. However, the G_ɑ4 subunit contains some unusual sequence divergences in residues highly conserved among most eukaryotic G_ɑ subunits, suggesting that G_ɑ4 may be a member of another class of G_ɑ subunits.