8IU0

Cryo-EM structure of the potassium-selective channelrhodopsin HcKCR1 H225F mutant in lipid nanodisc

Summary for 8IU0

• Entry DOI: 10.2210/pdb8iu0/pdb
• EMDB information: 35713
• Descriptor: HcKCR1, RETINAL, (7R,17E,20E)-4-HYDROXY-N,N,N-TRIMETHYL-9-OXO-7-[(PALMITOYLOXY)METHYL]-3,5,8-TRIOXA-4-PHOSPHAHEXACOSA-17,20-DIEN-1-AMINIUM 4-OXIDE, ... (5 entities in total)
• Functional Keywords: membrane protein, cryo-em
• Biological source: Hyphochytrium catenoides
• Total number of polymer chains: 1
• Total formula weight: 40309.61

Authors

Tajima, S.,Kim, Y.,Nakamura, S.,Yamashita, K.,Fukuda, M.,Deisseroth, K.,Kato, H.E. (deposition date: 2023-03-23, release date: 2023-09-06, Last modification date: 2024-11-06)

Primary citation

Tajima, S.,Kim, Y.S.,Fukuda, M.,Jo, Y.,Wang, P.Y.,Paggi, J.M.,Inoue, M.,Byrne, E.F.X.,Kishi, K.E.,Nakamura, S.,Ramakrishnan, C.,Takaramoto, S.,Nagata, T.,Konno, M.,Sugiura, M.,Katayama, K.,Matsui, T.E.,Yamashita, K.,Kim, S.,Ikeda, H.,Kim, J.,Kandori, H.,Dror, R.O.,Inoue, K.,Deisseroth, K.,Kato, H.E.
Structural basis for ion selectivity in potassium-selective channelrhodopsins.
Cell, 186:4325-4344.e26, 2023

PubMed Abstract: KCR channelrhodopsins (K-selective light-gated ion channels) have received attention as potential inhibitory optogenetic tools but more broadly pose a fundamental mystery regarding how their K selectivity is achieved. Here, we present 2.5-2.7 Å cryo-electron microscopy structures of HcKCR1 and HcKCR2 and of a structure-guided mutant with enhanced K selectivity. Structural, electrophysiological, computational, spectroscopic, and biochemical analyses reveal a distinctive mechanism for K selectivity; rather than forming the symmetrical filter of canonical K channels achieving both selectivity and dehydration, instead, three extracellular-vestibule residues within each monomer form a flexible asymmetric selectivity gate, while a distinct dehydration pathway extends intracellularly. Structural comparisons reveal a retinal-binding pocket that induces retinal rotation (accounting for HcKCR1/HcKCR2 spectral differences), and design of corresponding KCR variants with increased K selectivity (KALI-1/KALI-2) provides key advantages for optogenetic inhibition in vitro and in vivo. Thus, discovery of a mechanism for ion-channel K selectivity also provides a framework for next-generation optogenetics.

PubMed: 37652010
DOI: 10.1016/j.cell.2023.08.009

Experimental method

ELECTRON MICROSCOPY (2.66 Å)