Channel Gating in Kalium Channelrhodopsin Slow Mutants.
J Mol Biol
; 436(5): 168298, 2024 Mar 01.
Article
em En
| MEDLINE
| ID: mdl-37802216
ABSTRACT
Kalium channelrhodopsin 1 from Hyphochytrium catenoides (HcKCR1) is the first discovered natural light-gated ion channel that shows higher selectivity to K+ than to Na+ and therefore is used to silence neurons with light (optogenetics). Replacement of the conserved cysteine residue in the transmembrane helix 3 (Cys110) with alanine or threonine results in a >1,000-fold decrease in the channel closing rate. The phenotype of the corresponding mutants in channelrhodopsin 2 is attributed to breaking of a specific interhelical hydrogen bond (the "DC gate"). Unlike CrChR2 and other ChRs with long distance "DC gates", the HcKCR1 structure does not reveal any hydrogen bonding partners to Cys110, indicating that the mutant phenotype is likely caused by disruption of direct interaction between this residue and the chromophore. In HcKCR1_C110A, fast photochemical conversions corresponding to channel gating were followed by dramatically slower absorption changes. Full recovery of the unphotolyzed state in HcKCR1_C110A was extremely slow with two time constants 5.2 and 70 min. Analysis of the light-minus-dark difference spectra during these slow processes revealed accumulation of at least four spectrally distinct blue light-absorbing photocycle intermediates, L, M1 and M2, and a UV light-absorbing form, typical of bacteriorhodopsin-like channelrhodopsins from cryptophytes. Our results contribute to better understanding of the mechanistic links between the chromophore photochemistry and channel conductance, and provide the basis for using HcKCR1_C110A as an optogenetic tool.
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Texto completo:
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Rhinosporidium
/
Ativação do Canal Iônico
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Optogenética
/
Channelrhodopsins
Limite:
Humans
Idioma:
En
Revista:
J Mol Biol
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Estados Unidos