3.E.1.6.13
Viral rhodopsin II (RhoII) of 211 aas and 7 TMSs, OLPVRII, a VirChR1, a Na⁺/K⁺ channel that does not transport Ca²⁺. It forms a pentamer, with a symmetrical, bottle-like central channel with the narrow vestibule in the cytoplasmic part covered by a ring of 5 arginines, whereas 5 phenylalanines form a hydrophobic barrier in its exit (Bratanov et al. 2019). The proton donor, E42, is in helix B. The structure is unique among known rhodopsins. Structural and functional data and molecular dynamics suggest that OLPVRII might be a light-gated pentameric ion channel analogous to pentameric ligand-gated ion channels. A photon (hν) causes neural firing.  The 1.4 Å structure has been determined revealing a unique ion transport pathway through the protein (Zabelskii et al. 2020).