<i>Cis</i>–<i>Trans</i> Reisomerization Precedes Reprotonation of the Retinal Chromophore in the Photocycle of Schizorhodopsin 4

Hayashi, Kouhei; Mizuno, Maya; Kandori, Hideki; Mizutani, Yasuhisa

doi:10.1002/anie.202203149

Cited by 11 publications

(24 citation statements)

References 38 publications

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“…Figure shows the resonance Raman spectra of the sample 18–19 h after the addition of Ret5.12 in H 2 O and D 2 O buffers. The Raman band at 1631 cm –1 is unlikely due to CN stretching mode of the deprotonated Schiff base since the frequency was significantly higher than the frequency reported for the deprotonated all- trans Schiff base chromophore . The 1631 cm –1 band in H 2 O buffer did not show a deuteration shift in D 2 O buffer.…”

Section: Resultsmentioning

confidence: 70%

“…The Raman band at 1631 cm −1 is unlikely due to C�N stretching mode of the deprotonated Schiff base since the frequency was significantly higher than the frequency reported for the deprotonated all-trans Schiff base chromophore. 43 The 1631 cm −1 band in H 2 O buffer did not show a deuteration shift in D 2 O buffer. This indicates that the band is not due to the C�N stretching mode of the protonated Schiff base but rather is likely due to the C�O stretching mode of the retinal aldehyde moiety, and that Ret5.12 probably occupied the retinal binding pocket but had not formed a Schiff base linkage with the protein.…”

Section: ■ Results and Discussionmentioning

confidence: 92%

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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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Section: Resultsmentioning

confidence: 70%

Section: ■ Results and Discussionmentioning

confidence: 92%

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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“…Time-resolved ultraviolet resonance Raman (UVRR) spectroscopic measurements were carried out using the dual-beam rapid-flow method, and the delay times were controlled by the distance between the irradiating pump and probe lights . The experimental apparatus is described in Figure S1 in the Supporting Information, which was reported elsewhere and used here with some modifications. , The fourth harmonic of the output of a Ti:sapphire laser (Photonics Industries, TU-L) provided the 233 nm probe light to selectively observe Raman bands of the Trp and Tyr residues in the protein taking advantage of resonance Raman effect. The probe laser power was set to 0.5 mW (pulse energy 0.5 μJ, pulse width 30 ns, repetition rate 1 kHz).…”

Section: Methodsmentioning

confidence: 99%

Contact-Mediated Retinal–Opsin Coupling Enables Proton Pumping in Gloeobacter Rhodopsin

et al. 2022

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When a chromophore embedded in a photoreceptive protein undergoes a reaction upon photoexcitation, the photoreaction triggers structural changes in the protein moiety that are necessary for the function of the protein. It is thus essential to elucidate the coupling between the chromophore and protein moiety to understand the functional mechanism for photoreceptive proteins, but the mechanism by which this coupling occurs remains poorly understood. Here, we show that nonbonded atomic contacts play an essential role in driving functionally important structural changes following photoisomerization of the chromophore in Gloeobacter rhodopsin (GR). Time-resolved ultraviolet resonance Raman spectroscopy revealed that the substitution of Trp222, which contacts with methyl groups of the retinal chromophore, with a Phe residue reduced the extent of structural change. The proton-pumping activity of the GR mutant was as small as 9% of that of the wild type. Time-resolved visible absorption and resonance Raman spectra showed that the photocycle of the mutant proceeded to the L intermediate following the all-trans to 13-cis photoisomerization step but did not result in the deprotonation of the chromophore. The present results demonstrate that the atomic contacts between the chromophore and the Trp222 side chain induce the structural changes necessary for proton transfer. The requirement for dense atomic packing in a protein structure for the efficient propagation of structural changes through a coupling mechanism is discussed.

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“…During the recovery of the initial visible-absorbing state from M 3 , H + binds to the RSB from the extracellular side. Interestingly, Dr. Mizutani and his colleagues observed 13- cis -to-all- trans isomerization of the RSB in schizorhodopsin 4 (SzR4) during the accumulation of the M 3 . This process changes the orientation of the lone-pair electrons in the nitrogen atom of the RSB from the cytoplasmic side to the extracellular side, enabling the RSB to accept H + from the extracellular side.…”

Section: Photochemisty Of Retinal In Microbial Rhodopsinsmentioning

confidence: 99%

Photochemistry of the Retinal Chromophore in Microbial Rhodopsins

Inoue

2023

J. Phys. Chem. B

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Microbial rhodopsins are photoreceptive membrane proteins of microorganisms that express diverse photobiological functions. All-trans-retinylidene Schiff base, the so-called all-trans-retinal, is a chromophore of microbial rhodopsins, which captures photons. It isomerizes into the 13-cis form upon photoexcitation. Isomerization of retinal leads to sequential conformational changes in the protein, giving rise to active states that exhibit biological functions. Despite the rapidly expanding diversity of microbial rhodopsin functions, the photochemical behaviors of retinal were considered to be common among them. However, the retinal of many recently discovered rhodopsins was found to exhibit new photochemical characteristics, such as highly red-shifted absorption, isomerization to 7-cis and 11-cis forms, and energy transfer from a secondary carotenoid chromophore to the retinal, which is markedly different from that established in canonical microbial rhodopsins. Here, I review new aspects of retinal found in novel microbial rhodopsins and highlight the emerging problems that need to be addressed to understand noncanonical retinal photochemistry.

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

Cited by 11 publications

References 38 publications

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

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

Contact-Mediated Retinal–Opsin Coupling Enables Proton Pumping in Gloeobacter Rhodopsin

Photochemistry of the Retinal Chromophore in Microbial Rhodopsins

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