Independent HHsearch, Needleman-Wunsch-based, and motif analyses reveal the overall hierarchy for most of the G protein-coupled receptor families

• Several families of G protein-coupled receptors (GPCR) show no significant sequence similarities and it has been debated which groups of GPCRs that share a common origin. We developed and performed integrated independent HHsearch, Needleman-Wunsch-based and motif analyses on almost 7000 unique GPCRs from twelve species. Moreover, we mined the evolutionary important Trichoplax adhaerens, Nematostella vectensis, Thalassiosira pseudonana and Strongylocentrotus purpuratus genomes, revealing remarkably rich vertebrate-like repertoires already in the early Metazoan species. We found strong evidence for that the Adhesion and Frizzled families are children to the cAMP family with HHsearch homology probabilities of 99.8% and 99.4%, respectively, also supported by the Needleman-Wunsch analysis and several motifs. We also found that the large Rhodopsin family is likely a child of the cAMP family with a HHsearch homology probability of 99.4% and conserved motifs. Therefore, we suggest that the Adhesion and Frizzled families originated from the cAMP family in an event close to that which gave rise to the Rhodopsin family. We also found convincing evidence that the Rhodopsin family is parent to the important sensory Taste 2, Vomeronasal type 1 and Nematode chemoreceptor families. The insect odorant, gustatory and Trehalose receptors, frequently referred to as GPCRs, form a separate cluster without relationship to the other families and we speculate, based on these and other’s results, that these families are ligand-gated ion channels rather than GPCRs. Overall, we suggest common descent of at least 97% of the GPCRs sequences found in humans, including all the main families.

Nyckelord

evolution

GPCR

GPCRs

G-protein

7TM

Rhodopsin

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