Strongly Hydrogen-Bonded Schiff Base and Adjoining Polyene Twisting in the Retinal Chromophore of Schizorhodopsins

Shionoya, Tomomi; Singh, Manish Pratap; Mizuno, Maya; Kandori, Hideki; Mizutani, Yasuhisa

doi:10.1021/acs.biochem.1c00529

Cited by 12 publications

(34 citation statements)

References 35 publications

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“…An approximately linear relationship exists between λ max and the peak frequency of the CC stretching bands of the retinal chromophores Figure S4 shows the λ max and the peak frequency of the CC stretching bands of the retinal chromophores in the microbial rhodopsins, model compounds, and C1C2 obtained in this study. − The λ max and peak frequency of the CC stretching bands obtained in this study are in good agreement with the linear relationship. This proves that the time-resolved resonance Raman measurements in this study accurately measured the retinal chromophore structure in each state.…”

Section: Resultssupporting

confidence: 82%

Twisting and Protonation of Retinal Chromophore Regulate Channel Gating of Channelrhodopsin C1C2

et al. 2023

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Channelrhodopsins (ChRs) are light-gated ion channels and central optogenetic tools that can control neuronal activity with high temporal resolution at the single-cell level. Although their application in optogenetics has rapidly progressed, it is unsolved how their channels open and close. ChRs transport ions through a series of interlocking elementary processes that occur over a broad time scale of subpicoseconds to seconds. During these processes, the retinal chromophore functions as a channel regulatory domain and transfers the optical input as local structural changes to the channel operating domain, the helices, leading to channel gating. Thus, the core question on channel gating dynamics is how the retinal chromophore structure changes throughout the photocycle and what rate-limits the kinetics. Here, we investigated the structural changes in the retinal chromophore of canonical ChR, C1C2, in all photointermediates using time-resolved resonance Raman spectroscopy. Moreover, to reveal the rate-limiting factors of the photocycle and channel gating, we measured the kinetic isotope effect of all photoreaction processes using laser flash photolysis and laser patch clamp, respectively. Spectroscopic and electrophysiological results provided the following understanding of the channel gating: the retinal chromophore highly twists upon the retinal Schiff base (RSB) deprotonation, causing the surrounding helices to move and open the channel. The ion-conducting pathway includes the RSB, where inflowing water mediates the proton to the deprotonated RSB. The twisting of the retinal chromophore relaxes upon the RSB reprotonation, which closes the channel. The RSB reprotonation rate-limits the channel closing.

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Section: Resultssupporting

confidence: 82%

Twisting and Protonation of Retinal Chromophore Regulate Channel Gating of Channelrhodopsin C1C2

et al. 2023

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“…The pD of the D 2 O buffer was also set to 8.0. The resonance Raman measurements were performed as described previously . Briefly, a 532 nm probe light with a typical energy of 0.5 mW at the sample position was the output of a single-frequency continuous wave diode-pumped solid-state (CW DPSS) laser (Cobolt, 04-01 Samba).…”

Section: Methodsmentioning

confidence: 99%

“…The resonance Raman measurements were performed as described previously. 20 Briefly, a 532 nm probe light with a typical energy of 0.5 mW at the sample position was the output of a single-frequency continuous wave diodepumped solid-state (CW DPSS) laser (Cobolt, 04-01 Samba). The sample solution was placed in a Ø10 mm glass tube used as a rotating cell, and the 90°scattered Raman light was collected and focused onto the entrance slit of a spectrograph (iHR320, HORIBA Jobin Yvon).…”

Section: ■ Introductionmentioning

confidence: 99%

Origin of a Double-Band Feature in the Ethylenic C═C Stretching Modes of the Retinal Chromophore in Heliorhodopsins

et al. 2022

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Photoreceptor proteins play a critical role in light utilization for energy conversion and environmental sensing. Rhodopsin is a prototypical photoreceptor protein containing a retinal group that functions as a light-receptive site. It is essential to characterize the structure of the retinal chromophore because the chromophore structure, along with retinal–protein interactions, regulates which wavelengths of light are absorbed. Resonance Raman spectroscopy is a powerful tool to characterize chromophore structures in proteins. The resonance Raman spectra of heliorhodopsins, a recently discovered rhodopsin family, were previously reported to exhibit two intense ethylenic CC stretching bands never observed for type-1 rhodopsins. Here, we show that the double-band feature in the ethylenic CC stretching modes is not due to structural inhomogeneity but rather to the retinal polyene chain’s linear structure. It contrasts with bent all-trans chromophore in type-1 rhodopsins. The linear structure of the chromophore results from weak atomic contacts between the 13-methyl group and a nearby Trp side chain, which can slow thermal reisomerization in the photocycle. It is possible that the deceleration of reisomerization increases the lifetime of the signaling intermediate for photosensory function.

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“…In SzR4, F70 and D184 are homologous to D85 and D212 in BR, respectively [7] . D184 is directly hydrogen‐bonded to the protonated Schiff base [7, 37] . In the cytoplasmic side of the Schiff base, E81 in SzR4 is homologous to D96 in BR.…”

Section: Figurementioning

confidence: 99%

“…[7] D184 is directly hydrogen-bonded to the protonated Schiff base. [7,37] In the cytoplasmic side of the Schiff base, E81 in SzR4 is homologous to D96 in BR. For SzR AM_5S_00009, no amino acid residue was identified as a metastable proton acceptor or proton donor.…”

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confidence: 99%

Cis–Trans Reisomerization Precedes Reprotonation of the Retinal Chromophore in the Photocycle of Schizorhodopsin 4

et al. 2022

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Recent discoveries of light-driven inward proton-pumping rhodopsins have opened new avenues to exploring the mechanism of unidirectional transport because these proteins transport protons in the opposite direction to conventional proton-pumping rhodopsins, despite their similar protein structure and membrane topology. Schizorhodopsin (SzR) is a newly discovered rhodopsin family of light-driven inward proton pumps.Here, we report time-resolved resonance Raman spectra showing that cis-trans thermal reisomerization precedes reprotonation at the Schiff base of the retinal chromophore in the photocycle of SzR AM_5_00977. This sequence has not been observed for the photocycles of conventional proton-pumping rhodopsins, in which reisomerization follows reprotonation, and thus provides insights into the mechanism of proton uptake to the chromophore during inward proton pumping. The present findings are expected to contribute to controlling the direction of proton transport in engineered proteins.

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Strongly Hydrogen-Bonded Schiff Base and Adjoining Polyene Twisting in the Retinal Chromophore of Schizorhodopsins

Cited by 12 publications

References 35 publications

Twisting and Protonation of Retinal Chromophore Regulate Channel Gating of Channelrhodopsin C1C2

Twisting and Protonation of Retinal Chromophore Regulate Channel Gating of Channelrhodopsin C1C2

Origin of a Double-Band Feature in the Ethylenic C═C Stretching Modes of the Retinal Chromophore in Heliorhodopsins

Cis–Trans Reisomerization Precedes Reprotonation of the Retinal Chromophore in the Photocycle of Schizorhodopsin 4

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