1.A.69.4.4
Odorant (pheromone) receptor, OR-3, BmOR3, Or-3, PR-3, of 439 aas and 7 TMSs in a 2 + 1 + 2 + 2 TMS arrangement. The activation of PRs is coupled to the calcium permeability of their coreceptor (Orco (see TC# 1.A.69.1.1)) or putatively with G proteins (Lin et al. 2021). Using the PR BmOR3 from the silk moth B. mori and its coreceptor BmOrco as a template, Lin et al. 2021 showed that an agonist-induced conformational change of BmOR3 is transmitted to BmOrco through TMS7s of both receptors, resulting in the activation of BmOrco. Key interactions, including an ionic lock and a hydrophobic zipper, are essential for mediating the functional coupling between BmOR3 and BmOrco. BmOR3 also selectively coupled with Gi proteins, which is dispensable for BmOrco coupling. Moreover, trans-7TM BmOR3 recruited arrestin (see TC# 8.A.136) in an agonist-dependent manner, which indicated an important role for BmOR3-BmOrco complex formation in ionotropic functions. Thus, the coupling of G protein and arrestin to a prototype trans-7TMS PR, BmOR3, has been demonstrated (Lin et al. 2021).