MRGX2
MRGX2 is a G-protein-coupled receptor. It is specifically expressed in the sensory neurons of the human peripheral nervous system and involved in nociception.
Human evolution
MRGX2 had undergone adaptive changes in the path of human evolution, which were likely caused by Darwinian positive selection. The patterns of DNA sequence polymorphisms in human populations showed an excess of derived substitutions, which against the expectation of neutral evolution, implying that the adaptive evolution of MRGX2 in humans was a relatively recent event. (#15862286#)
The reconstructed secondary structure of the human MRGX2 revealed that three of the four human-specific amino acid substitutions were located in the extra-cellular domains. Such critical substitutions may alter the interactions between MRGX2 protein and its ligand, thus, potentially led to adaptive changes of the pain-perception-related nervous system during human evolution. (#15862286#)
References
Yang S, Liu Y, Lin AA, Cavalli-Sforza LL, Zhao Z, Su B. Adaptive evolution of MRGX2, a human sensory neuron specific gene involved in nociception. Gene. 2005 Jun 6;352:30-5. PMID: #15862286#