Resonance Raman Spectra of Red-Shifted Retinal Schiff’s Base

Sugihara, Toshiharu; Kitagawa, Teizo

doi:10.1246/bcsj.59.2929

Cited by 6 publications

(6 citation statements)

References 15 publications

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“…Previous studies of retinal proteins and model compounds of the retinal chromophore have established that there is an empirical inverse linear correlation between the ν(CC) frequency and the absorption maximum of the retinal chromophore. − Furthermore, the wavelength of the absorption maximum of the solubilized TR subjected to heat treatment (524 nm) was 6 nm shorter compared to the same sample without the treatment (530 nm) . The present observed difference in the ν(CC) frequency is consistent with the difference in the absorption maximum wavelength reported for TR, indicating an increase of bond alternation of the polyene chain in the chromophore upon monomerization.…”

Section: Resultssupporting

confidence: 88%

High Thermal Stability of Oligomeric Assemblies of Thermophilic Rhodopsin in a Lipid Environment

et al. 2018

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Thermophilic rhodopsin (TR) is a light-driven proton pump from the extreme thermophile Thermus thermophilus JL-18. Previous studies on TR solubilized with detergent showed that the protein exhibits high thermal stability and forms a trimer at room temperature but irreversibly dissociates into monomers when incubated at physiological temperature (75 °C). In the present study, we used resonance Raman (RR) spectroscopy, solid-state NMR spectroscopy, and high-speed atomic force microscopy to analyze the oligomeric structure of TR in a lipid environment. The obtained spectra and microscopic images demonstrate that TR adopts a pentameric form in a lipid environment and that this assembly is stable at the physiological temperature, in contrast to the behavior of the protein in the solubilized state. These results indicate that the thermal stability of the oligomeric assembly of TR is higher in a lipid environment than in detergent micelles. The observed RR spectra also showed that the retinal chromophore is strongly hydrogen bonded to an internal water molecule via a protonated Schiff base, which is characteristic of proton-pumping rhodopsins. The obtained data strongly suggest that TR functions in the pentameric form at physiological temperature in the extreme thermophile T. thermophilus JL-18. We utilized the high thermal stability of the monomeric form of solubilized TR and here report the first RR spectra of the monomeric form of a microbial rhodopsin. The observed RR spectra revealed that the monomerization of TR alters the chromophore structure: there are changes in the bond alternation of the polyene chain and in the hydrogen-bond strength of the protonated Schiff base. The present study revealed the high thermal stability of oligomeric assemblies of TR in the lipid environment and suggested the importance of using TR embedded in lipid membrane for elucidation of its functional mechanism.

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Section: Resultssupporting

confidence: 88%

High Thermal Stability of Oligomeric Assemblies of Thermophilic Rhodopsin in a Lipid Environment

et al. 2018

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“…1655 cm"1, while in hexafluoro-2-propanol (HFIP) it appears at 1644 cm"1. Similar shifts in fluorinated alcohols were observed recently in resonance Raman studies (Sugihara & Kitagawa, 1986).…”

Section: Wavenumberssupporting

confidence: 88%

Factors affecting the C:N stretching in protonated retinal Schiff base: a model study for bacteriorhodopsin and visual pigments

Baasov¹,

Friedman²,

Sheves³

1987

Biochemistry

170

189

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Factors affecting the C = N stretching frequency of protonated retinal Schiff base (RSBH+) were studied with a series of synthetic chromophores and measured under different conditions. Interaction of RSBH+ with nonconjugated positive charges in the vicinity of the ring moiety or a planar polyene conformation (in contrast to the twisted retinal conformation in solution) shifted the absorption maxima but did not affect the C = N stretching frequency. The latter, however, was affected by environmental perturbations in the vicinity of the Schiff base linkage. Diminished ion pairing (i.e., of the positively charged nitrogen to its anion) achieved either by substituting a more bulky counteranion or by designing models with a homoconjugation effect lowered the C = N stretch energy. Decreasing solvation of the positively charged nitrogen leads to a similar trend. These effects in the vicinity of the Schiff base linkage also perturb the deuterium isotope effect observed upon deuteriation of the Schiff base. The results are interpreted by considering the mixing of the C = N stretching and C = N-H bending vibration. The C = N mode is shifted due to electrostatic interaction with nonconjugated positive charges in the vicinity of the Schiff base linkage, an interaction that does not influence the isotope effect. Weak hydrogen bonding between the Schiff base linkage in bacteriorhodopsin (bR) and its counteranion or, alternatively, poor solvation of the positively charged Schiff base nitrogen can account for the C = N stretching frequency of 1640 cm-1 and the deuterium isotope effect of 17 cm-1 observed in this pigment.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…The shoulder band at 1558 cm –1 was assigned to the N intermediate and was not attributed to the O intermediate. There is an empirical inverse linear correlation between the CC stretching frequency and the absorption maximum of the retinal chromophore. − A frequency of 1558 cm –1 is too high to be assigned to the O intermediate: the CC stretching frequency in the O intermediate, with the absorption maximum at 600 nm, would be lower than that in the unphotolyzed state with the absorption maximum at 575 nm, as observed in the photocycles of BR and s HR . In addition, the 475 nm probe light was poorly resonant with the electronic transition of the red-shifted O intermediate.…”

Section: Resultsmentioning

confidence: 99%

“…In the time-resolved RR spectra of the retinal chromophore in p HR (Figure ), we found three distinct CC stretch bands attributed to different intermediates. The CC stretching frequency in the retinal chromophore linearly correlates with its absorption maximum wavelength; − consequently, this band is a marker that can be used to determine the intermediate states. Based on temporal intensity changes in the CC stretch bands, SVD analysis was conducted for spectral changes in the CC stretch bands in addition to spectral changes in the C–C stretch bands (Figures S5 and S6 in the Supporting Information).…”

Section: Discussionmentioning

confidence: 99%

Structural Evolution of a Retinal Chromophore in the Photocycle of Halorhodopsin from Natronobacterium pharaonis

et al. 2018

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We revealed the chloride ion pumping mechanism in halorhodopsin from Natronobacterium pharaonis ( pHR) by exploring sequential structural changes in the retinal chromophore during its photocycle using time-resolved resonance Raman (RR) spectroscopy on the nanosecond to millisecond time scales. A series of RR spectra of the retinal chromophore in the unphotolyzed state and of the three intermediates of pHR were obtained. Using singular value decomposition analysis of the C═C and C-C stretch bands in the time-resolved RR spectra, we identified the spectra of the K, L, and N intermediates. We focused on structural markers of the RR bands to explore the structure of the retinal chromophore. In the unphotolyzed state, the retinal chromophore is in the planar all- trans, 15- anti geometry. The bound ion affects the polyene chain but does not interact with the protonated Schiff base. In the observed intermediates, the chromophore is in the 13- cis configuration. The chromophore in the K intermediate is distorted due to the photoisomerization of retinal. The hydrogen bond is weak in the unphotolyzed state and in the K intermediate, resulting in exchange of the hydrogen-bond acceptor to a water molecule in the K-to-L transition, relaxation of the polyene chain distortion, and generation of an alternative distortion near the Schiff base. The bound halide ion interacts with the protonated Schiff base through the water molecule bound to the protonated Schiff base. In the L-to-N transition, the hydrogen acceptor of the protonated Schiff base switches from the water molecule to another species, although the strong hydrogen bond of the protonated Schiff base remains. This paper reports the first observation of sequential changes in the RR spectra in the pHR photocycle, provides information on the structural evolution of the retinal chromophore, and proposes a model for chloride ion translocation in pHR.

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Resonance Raman Spectra of Red-Shifted Retinal Schiff’s Base

Cited by 6 publications

References 15 publications

High Thermal Stability of Oligomeric Assemblies of Thermophilic Rhodopsin in a Lipid Environment

High Thermal Stability of Oligomeric Assemblies of Thermophilic Rhodopsin in a Lipid Environment

Factors affecting the C:N stretching in protonated retinal Schiff base: a model study for bacteriorhodopsin and visual pigments

Structural Evolution of a Retinal Chromophore in the Photocycle of Halorhodopsin from Natronobacterium pharaonis

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