Identification of Dictyostelium Ga 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 Gα genes, Gα4 and Gα5, that are developmentally regulated. Transcripts from both of these genes are primarily expressed during the multkellular stages of development, suggesting possible roles in cell differentiation or morphogenesis. The entire Gα4 gene was sequenced and found to encode a protein consisting of 345 amino acids. The Gα4 subunit is homologous to other previously identified Gα subunits, including the Dic-tyostelium Gα1 (43% identity) and Gα2 (41% identity) subunit. However, the Gα4 subunit contains some unusual sequence divergences in residues highly conserved among most eukaryotic Gα subunits, suggesting that Gα4 may be a member of another class of Gα subunits.