Rhodopsin-bestrophin fusion proteins from unicellular algae form gigantic pentameric ion channels.
Andrey RozenbergIgor KaczmarczykDonna MatzovJohannes VierockTakashi NagataMasahiro SugiuraKota KatayamaYuma KawasakiMasae KonnoYujiro NagasakaMako AoyamaIshita DasEfrat PahimaJonathan Richard ChurchSuliman AdamVeniamin A BorinAriel ChazanSandra AugustinJonas WietekJulien DineYoav PelegAkira KawanabeYuichiro FujiwaraOfer YizharMordechai ShevesIgor SchapiroYuji FurutaniHideki KandoriKeiichi InouePeter HegemannOded BéjàMoran Shalev-BenamiPublished in: Nature structural & molecular biology (2022)
Many organisms sense light using rhodopsins, photoreceptive proteins containing a retinal chromophore. Here we report the discovery, structure and biophysical characterization of bestrhodopsins, a microbial rhodopsin subfamily from marine unicellular algae, in which one rhodopsin domain of eight transmembrane helices or, more often, two such domains in tandem, are C-terminally fused to a bestrophin channel. Cryo-EM analysis of a rhodopsin-rhodopsin-bestrophin fusion revealed that it forms a pentameric megacomplex (~700 kDa) with five rhodopsin pseudodimers surrounding the channel in the center. Bestrhodopsins are metastable and undergo photoconversion between red- and green-absorbing or green- and UVA-absorbing forms in the different variants. The retinal chromophore, in a unique binding pocket, photoisomerizes from all-trans to 11-cis form. Heterologously expressed bestrhodopsin behaves as a light-modulated anion channel.