Interaction between the third intercellular loop of human $5-HT_6$ serotonin receptor and G protein alpha subunit

Serotonin (5-HT; 5-hydroxytryptamine) exerts multiple effects on central nervous system as well as behaviors such as mood and appetite. The signaling of serotonin is mediated by 7 families of serotonin receptors, designated 5-HT$_1$ to 5-HT$_{7}$. Six families of this receptor are G-protein coupled 7TM receptors, and the third intracellular loop of these receptors is proposed to interact with specific types of G-proteins. To investigate the specific interaction between the third intracellular loop of 5-HT$_{6}$ with G$\square$s, we have constructed a chimera protein that represent the third intracellular loop of 5-HT$_{6}$ within a leucine zipper motifs, In addition an alpha subunit of human G-protein that interact with 5-HT$_{6}$ was cloned into a bacterial expression vector. The two proteins were expressed in E. coli and purified in homogeneity. The interaction of the prepared proteins was examined by ELISA assay. The affinity between the two proteins and effect of insertion mutations were discussed.ussed.d.