Evolutionary analysis of G-proteins in early metazoans: cloning of alpha- and beta-subunits from the sponge Geodia cydonium.

摘要: G-protein-coupled (seven-transmembrane segment)-receptors represent a major group of metazoan receptors, involved in transduction extracellular signals. The G-proteins, which are made up Galpha/beta/gamma-subunits, link the receptors to effector system(s). To analyze phylogenetic relationships among alpha-subunits cDNAs were isolated from Geodia cydonium, marine sponge belonging lowest phylum, Porifera. One encodes putative isotype stimulator adenylyl cyclase (Galpha s), another one inhibitor i/o) and third activator phospholipase C q). In addition beta-subunit was cloned same species. deduced amino acid sequences Galpha s -(putative Mr 44749), i/o -(Mr 41064) q subunits (Mr 41363) found display high similarity with corresponding higher Metazoa, only distantly related those slime mold, yeast or plants. Of lower beta-subunits animals plants, thus not allowing robust grouping. These data demonstrate that relationships, obtained analyses alpha support conclusion all phyla, including Porifera monophyletic origin.