Halorhodopsin, a light-driven electrogenic chloride-transport system

Lanyi, Janos Κ.

doi:10.1152/physrev.1990.70.2.319

Cited by 124 publications

(78 citation statements)

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“…shifts as the cone opsins studied here (29). The Schiffbase environment in hR is homologous to that in bR: the residues corresponding to D212 and R82 of bR are conserved (D238 and R108 in hR); however, D85 in bR is replaced by T111 in hR (29). It seems likely, therefore, that the Schiff base counterion in hR consists of D238, R108, and an exchangeable (and transportable) Cl-ion, which takes the place of the lost carboxylate and hydrogen bonds to T111.…”

Section: Discussionmentioning

confidence: 75%

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Anion sensitivity and spectral tuning of cone visual pigments in situ.

Kleinschmidt

Hárosi

1992

Proc. Natl. Acad. Sci. U.S.A.

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We tested the effect of anions on the absorbance spectrum of native visual pigments as measured by microspectrophotometry in individual cone outer segments of four species of fish and one species of amphibian. In all species tested, the long-wavelength-absorbing cone pigments were anion sensitive, and their A.. could be tuned over a range of 55 nm depending on the identity of the anion present. Cl-and Br-were the only anions that produced native pigment spectra by red shifting A.. from its value under anion-free conditions. Lyotropic anions such as NO-, SCN-, BF4, and ClIO caused substantial and graded blue shifts of A... The apparent Kd of binding sites on the pigment for Cl-and for CIO4 was -2 mM. Taken together with previous findings on three visual pigments from the reptilian, avian, and amphibian classes, our results support the hypothesis that all long-wavelength-absorbing vertebrate visual pigments are spectrally tuned in part through the binding of a chloride ion. We propose that the site of anion tuning is near the protonated Schiff base of the chromophore, whose counterion may be complex and include Cl-as an exchangeable anion. This counterion configuration may resemble the one present in the light-driven Cl-pump halorhodopsin.Color vision in vertebrates is based on sets of two, three, or four different photopigments that reside in separate classes of cone photoreceptors. The wavelength of peak absorbance (Amax) of these pigments ranges from the UV (360 nm) to the far red (635 nm). All vertebrate visual pigments are integral membrane proteins and contain 11-cis-retinal or 11-cisdehydroretinal as the chromophore that is covalently bound through a Schiffbase linkage to a lysine residue on the protein (opsin) moiety ofthe pigment (1). Although great progress has been made in recent years in unraveling the structure of visual pigments, the molecular basis of spectral tuning is still only incompletely understood.A variety of mechanisms have been invoked to account for photopigment tuning (for reviews, see refs. 2 and 3). For example, protonation of the retinal Schiff base shifts Amax from 360 to 430 nm (4). Blue-absorbing pigments may contain an unperturbed chromophore behaving much like a protonated retinal Schiff base in a nonpolar solvent (5). Closer interaction of the chromophore with the protein perturbs the electronic structure of the chromophore and results in an additional red shift of Am,,,. This shift is commonly called the "opsin shift" and very likely comprises multiple components. For example, Amax is extremely sensitive to the charge environment provided by the counterion, which is paired with the protonated Schiff base (3). A decreased interaction between protonated Schiff base and counterion, perhaps caused by an increased distance between the two, may be responsible for the opsin shift in green-absorbing rhodopsins (Amax, "500 nm). Amino acid side chains, which form the hydrophobic binding pocket for the chromophore, also can interact with and perturb the chromophore. In fact, much ...

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Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 85%

Anion sensitivity and spectral tuning of cone visual pigments in situ.

Kleinschmidt

Hárosi

1992

Proc. Natl. Acad. Sci. U.S.A.

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“…Halorhodopsin is an opsin identified from Archaea which, when stimulated with yellow light, pumps chloride ions into cells [63646566676869]. When halorhodopsin is expressed in neurons, photostimulation promotes an influx of chloride ions that results in hyperpolarization and the inhibition of the firing of action potentials in the stimulated cells.…”

Section: Optogenetics and Chemogeneticsmentioning

confidence: 99%

Optogenetic and Chemogenetic Approaches for Studying Astrocytes and Gliotransmitters

2016

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The brain consists of heterogeneous populations of neuronal and non-neuronal cells. The revelation of their connections and interactions is fundamental to understanding normal brain functions as well as abnormal changes in pathological conditions. Optogenetics and chemogenetics have been developed to allow functional manipulations both in vitro and in vivo to examine causal relationships between cellular changes and functional outcomes. These techniques are based on genetically encoded effector molecules that respond exclusively to exogenous stimuli, such as a certain wavelength of light or a synthetic ligand. Activation of effector molecules provokes diverse intracellular changes, such as an influx or efflux of ions, depolarization or hyperpolarization of membranes, and activation of intracellular signaling cascades. Optogenetics and chemogenetics have been applied mainly to the study of neuronal circuits, but their use in studying non-neuronal cells has been gradually increasing. Here we introduce recent studies that have employed optogenetics and chemogenetics to reveal the function of astrocytes and gliotransmitters.

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“…Channelrhodopsins such as ChR2 and VChR1, transduced into retinal neurons, function as light-gated cation-selective channels and cause depolarization of the neurons by absorbing specific wavelengths of light. Halorhodopsin derived from Natronomonas pharaonis (NpHR) is a light-driven chloride pump (Lanyi 1990) and shows peak sensitivity to the wavelength of ∼580 nm (yellow). Thus, bidirectional control of neuronal firing can be possible by the transduction of both ChR2 and NpHR in the neurons, because of the difference in the excitation wavelength of the two ion pumps (ChR2, blue; NpHR, yellow) (Evanko 2007;Han and Boyden 2007;Zhang et al 2007a,b).…”

Section: Prospects Of Channelrhodopsinsmentioning

confidence: 99%

Channelrhodopsins provide a breakthrough insight into strategies for curing blindness

Tomita

Sugano

Isago

et al. 2009

J Genet

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Photoreceptor cells are the only retinal neurons that can absorb photons. Their degeneration due to some diseases or injuries leads to blindness. Retinal prostheses electrically stimulating surviving retinal cells and evoking a pseudo light sensation have been investigated over the past decade for restoring vision. Currently, a gene therapy approach is under development. Channelrhodopsin-2 derived from the green alga Chlamydomonas reinhardtii, is a microbial-type rhodopsin. Its specific characteristic is that it functions as a light-driven cation-selective channel. It has been reported that the channelrhodopsin-2 transforms inner light-insensitive retinal neurons to light-sensitive neurons. Herein, we introduce new strategies for restoring vision by using channelrhodopsins and discuss the properties of adeno-associated virus vectors widely used in gene therapy.

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Halorhodopsin, a light-driven electrogenic chloride-transport system

Cited by 124 publications

References 0 publications

Anion sensitivity and spectral tuning of cone visual pigments in situ.

Anion sensitivity and spectral tuning of cone visual pigments in situ.

Optogenetic and Chemogenetic Approaches for Studying Astrocytes and Gliotransmitters

Channelrhodopsins provide a breakthrough insight into strategies for curing blindness

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