Structure–Function Relationship of Channelrhodopsins

Kato, Hideaki E.

doi:10.1007/978-981-15-8763-4_3

Cited by 17 publications

(17 citation statements)

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“…Light-a crucial energy source and environmental signal-is typically captured by motile organisms using rhodopsins, which are largely classified into two groups: microbial and animal, both consisting of a seven-transmembrane (7TM) protein (opsin) and a covalently bound chromophore (retinal). Light absorption induces retinal isomerization followed by photocycle, a series of photochemical reactions (Zhang et al, 2011;Ernst et al, 2014;Deisseroth and Hegemann, 2017), which in microbial rhodopsins ultimately exerts direct biochemical action (examples include pumps, channels, sensors, and enzymes) (Kandori, 2020;Kato, 2021). Targeted expression of these proteins (especially of the channel-and pump-type) in specific cell types, when applied along with precise light delivery, enables causal study of cellular activity in behaving organisms (optogenetics) (Deisseroth, 2015(Deisseroth, , 2021Kurihara and Sudo, 2015).…”

Section: Introductionmentioning

confidence: 99%

Structural basis for channel conduction in the pump-like channelrhodopsin ChRmine

Kishi

Kim

Fukuda

et al. 2022

Cell

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Section: Introductionmentioning

confidence: 99%

Structural basis for channel conduction in the pump-like channelrhodopsin ChRmine

Kishi

Kim

Fukuda

et al. 2022

Cell

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“…During the photocycle, microbial rhodopsins occupy a series of discrete and spectroscopically-distinguishable intermediate states (e.g. K, L, M, N, O), and ultimately transduce the photon by directly exerting biochemical functionality (diverse subfamily members include ion pumps, ion channels, sensors, histidine kinases, adenylyl/guanylyl cyclases, and phosphodiesterases 7,8 ). Heterologous expression of these proteins (especially of the iontransporting channel-and pump-type rhodopsins) can be achieved by targeting the opsin genes to specific cell types, which (when applied along with precise light-delivery technology) enables high-speed control of the membrane potential of specific cells in behaving organisms with light.…”

Section: Introductionmentioning

confidence: 99%

Structural basis for channel conduction in the pump-like channelrhodopsin ChRmine

Kishi

Kim

Fukuda

et al. 2021

Preprint

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ChRmine, a recently-discovered bacteriorhodopsin-like cation-conducting channelrhodopsin, exhibits puzzling properties (unusually-large photocurrents, exceptional red-shift in action spectrum, and extreme light-sensitivity) that have opened up new opportunities in optogenetics. ChRmine and its homologs function as light-gated ion channels, but by primary sequence more closely resemble ion pump rhodopsins; the molecular mechanisms for passive channel conduction in this family of proteins, as well as the unusual properties of ChRmine itself, have remained mysterious. Here we present the cryo-electron microscopy structure of ChRmine at 2.0 Å resolution. The structure reveals striking architectural features never seen before in channelrhodopsins including trimeric assembly, a short transmembrane-helix 3 unwound in the middle of the membrane, a prominently-twisting extracellular-loop 1, remarkably-large intracellular cavities and extracellular vestibule, and an unprecedented hydrophilic pore that extends through the center of the trimer, separate from the three individual monomer pores. Electrophysiological, spectroscopic, and computational analyses provide insight into conduction and gating of light-gated channels with these distinct design features, and point the way toward structure-guided creation of novel channelrhodopsins for optogenetic applications in biology.

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“…Light-sensitive ion channels also exist in some unicellular algae that participate in phototaxis in green algae (chlorophytes) by depolarising the plasma membrane [ 274 , 275 ]. These channels, channelrhodopsins (737 aas), evolved from bacterio-rhodopsin consisting of seven transmembrane segments covalently linked to a retinal chromophore [ 276 ]. Light absorption induces isomerisation of the retinal, which, in turn, causes a set of conformational changes leading to the opening of a pore that allows ions to pass through [ 277 , 278 , 279 ].…”

Section: Cell Signalling and Sensory Motricitymentioning

confidence: 99%

Towards the Idea of Molecular Brains

Timsit

Sergeant-Perthuis

2021

IJMS

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How can single cells without nervous systems perform complex behaviours such as habituation, associative learning and decision making, which are considered the hallmark of animals with a brain? Are there molecular systems that underlie cognitive properties equivalent to those of the brain? This review follows the development of the idea of molecular brains from Darwin’s “root brain hypothesis”, through bacterial chemotaxis, to the recent discovery of neuron-like r-protein networks in the ribosome. By combining a structural biology view with a Bayesian brain approach, this review explores the evolutionary labyrinth of information processing systems across scales. Ribosomal protein networks open a window into what were probably the earliest signalling systems to emerge before the radiation of the three kingdoms. While ribosomal networks are characterised by long-lasting interactions between their protein nodes, cell signalling networks are essentially based on transient interactions. As a corollary, while signals propagated in persistent networks may be ephemeral, networks whose interactions are transient constrain signals diffusing into the cytoplasm to be durable in time, such as post-translational modifications of proteins or second messenger synthesis. The duration and nature of the signals, in turn, implies different mechanisms for the integration of multiple signals and decision making. Evolution then reinvented networks with persistent interactions with the development of nervous systems in metazoans. Ribosomal protein networks and simple nervous systems display architectural and functional analogies whose comparison could suggest scale invariance in information processing. At the molecular level, the significant complexification of eukaryotic ribosomal protein networks is associated with a burst in the acquisition of new conserved aromatic amino acids. Knowing that aromatic residues play a critical role in allosteric receptors and channels, this observation suggests a general role of π systems and their interactions with charged amino acids in multiple signal integration and information processing. We think that these findings may provide the molecular basis for designing future computers with organic processors.

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Structure–Function Relationship of Channelrhodopsins

Cited by 17 publications

References 104 publications

Structural basis for channel conduction in the pump-like channelrhodopsin ChRmine

Structural basis for channel conduction in the pump-like channelrhodopsin ChRmine

Structural basis for channel conduction in the pump-like channelrhodopsin ChRmine

Towards the Idea of Molecular Brains

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