Open AccessThe fifth class of Gα proteins
Author(s) -
Y. Oka,
Luís R. Saraiva,
Yen Yen Kwan,
Sigrun Korsching
Publication year - 2009
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0809420106
Subject(s) - biology , vertebrate , zebrafish , heterotrimeric g protein , homology (biology) , gene , genetics , conserved sequence , amino acid , protein family , evolutionary biology , peptide sequence , g protein , receptor
All α-subunits of vertebrate heterotrimeric G proteins have been classified into 4 major classes, Gs, Gi, Gq, and G12, which possess orthologs already in sponges, one of the earliest animal phyla to evolve. Here we report the discovery of the fifth class of Gα protein, Gv, ancient like the other 4 classes, with members already in sponges, and encoded by 1–2gnav genes per species. Gv is conserved across the animal kingdom including vertebrates, arthropods, mollusks, and annelids, but has been lost in many lineages such as nematodes, fruit fly, jawless fish, and tetrapods, concordant with a birth-and-death mode of evolution. All Gv proteins contain 5 G-box motifs characteristic of GTP-binding proteins and the expected acylation consensus sites in the N-terminal region. Sixty amino acid residues are conserved only among Gv, suggesting that they may constitute interaction sites for Gv-specific partner molecules. Overall Gv homology is high, on average 70% amino acid identity among vertebrate family members. Thed N /d S analysis of teleostgnav genes reveals evolution under stringent negative selection. Genomic structure of vertebrategnav genes is well conserved and different from those of the other 4 classes. The predicted full ORF of zebrafishgnav1 was confirmed by isolation from cDNA. RT-PCR analysis showed broad expression ofgnav1 in adult zebrafish and in situ hybridization demonstrated a more restricted expression in larval tissues including the developing inner ear. The discovery of this fifth class of Gα proteins changes our understanding of G protein evolution.