Assignment and interpretation of hydrogen out-of-plane vibrations in the resonance Raman spectra of rhodopsin and bathorhodopsin

Eyring, Gregory; Curry, Bostick; Broek, Albert; Lugtenburg, J.; Mathies, Richard A.

doi:10.1021/bi00531a028

Cited by 212 publications

(321 citation statements)

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“…This was confirmed by application of low temperature CD (8)(9)(10), laser Raman (11), and Fourier transform IR (12) spectroscopies. Since photorhodopsin cannot be stabilized at low temperature, its chromophore conformation could not be investigated by means of low temperature spectroscopies applied for that of bathorhodopsin.…”

mentioning

confidence: 58%

Photoisomerization mechanism of the rhodopsin chromophore: picosecond photolysis of pigment containing 11-cis-locked eight-membered ring retinal.

Mizukami

Kandori

Shichida

et al. 1993

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

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The primary photochemical event in rhodopsin is an l1-cis to 11-trans photoisomerization of its retinylidene chromophore to form the primary intermediate photorhodopsin. Earlier picosecond studies have shown that no intermediate is formed when the retinal li-ene is fixed through a bridging five-membered ring, whereas a photorhodopsin-like intermediate is formed when it is fixed through a flexible seven-membered ring. Results from a rhodopsin analog formed from a retinal with locked l1-ene structure through the more flexible eight-membered ring (Ret8) are described. Incubation of bovine opsin with Ret8 formed two pigments absorbing at 425 nm (P425) and 500 nm (P500). P425, however, is an artifact because it formed from thermally denatured opsin or other proteins and Ret8. Excitation of P500 with a picosecond green pulse led to formation of two intermediates corresponding to photo-and bathorhodopsins. These results demonstrate that an appearance of early intermediates is dependent on the flexibility of the ll-ene and that the photoisomerization of P500 proceeds by stepwise changes of chromophore-protein interaction, which in turn leads to a relaxation of the highly twisted all-trans-retinylidene chromophore in photorhodopsin.The rod photoreceptor cell, responsible for scotopic vision, is a highly sensitive biological photosensor reflecting the high photosensitivity of the visual pigment rhodopsin. Rhodopsin contains an 11-cis-retinal chromophore ( Fig. 1) bound via a protonated Schiff base linkage to Lys-296 of the apoprotein opsin. Since the initial event of rhodopsin after absorption of a photon is a cis-to-trans isomerization of the chromophore (1) with a high quantum yield (2) The conformation of the retinylidene chromophore of bathorhodopsin had been speculated as a twisted all-trans form (4). This was confirmed by application of low temperature CD (8-10), laser Raman (11), and Fourier transform IR (12) spectroscopies. Since photorhodopsin cannot be stabilized at low temperature, its chromophore conformation could not be investigated by means of low temperature spectroscopies applied for that of bathorhodopsin. Therefore, it was investigated by means of picosecond laser photolysis with the aid of rhodopsin analogs (Rh7 and RhS), each of which has a chromophore (Ret7 or Ret5; sbe Fig. 1) that locked the 11-ene in a cis configuration with the trimethylene or methylene bridge, respectively (13)(14)(15). The two retinal analogs differ in flexibility of the ring around the 11-ene from each other. Namely, the seven-membered ring in Ret7 is relatively flexible, whereas the five-membered ring in Ret5 is held in a rigid planar structure. The excitation of Rh7 gave rise to an intermediate corresponding to photorhodopsin, whereas that of Rh5 led only to an excited state (15). Thus, it is suggested that the conversion of rhodopsin to photorhodopsin is due to the twist of the 11-ene and nearby single bonds and resulted in formation of a highly twisted all-trans chromophore. On the other hand, the excitation of Rh...

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mentioning

confidence: 58%

Photoisomerization mechanism of the rhodopsin chromophore: picosecond photolysis of pigment containing 11-cis-locked eight-membered ring retinal.

Mizukami

Kandori

Shichida

et al. 1993

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

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“…C-H (N-H) out-of-plane modes lie between 800 and 1000 cm-'. The appearance of intense RR bands in this region has been interpreted as a sign for considerable conformational distortion (13,19,20). In the spectra of BR-570 a few weak bands of this type are observed between 820 and 960 cm-' .…”

Section: Resultsmentioning

confidence: 99%

Structure of bacteriorhodopsin in the acidified membrane and at high ionic strength: resonance Raman study

Massig¹,

Stockburger

Alshuth

1985

Can. J. Chem.

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Resonance Raman (RR) spectra of the retinylidene Schiffs base (SB) chromophore of bacteriorhodopsin (BR) were obtained from purple membrane (PM) suspensions of Halobacteriumhalobium in three different equilibrium states: (1) the native state at neutral pH; (2) BR-605, the acidified membrane at pH 2; (3) BR-565(Cl−) or BR-545 (F−), at low pH and high ionic strength. In the native state the retinyl chromophore is stabilized by an ion-pair complex of the protonated SB group with a negative carboxylate counterion (A−) of the protein, giving [Formula: see text]. In the acidic form, BR-605, it is inferred from the RR spectra that the chromophore is immobilized. This is ascribed to a breakdown of the ionic interaction by protonation of A−. In the two (3) forms the RR spectra show that the original structure of the chromophore in the native state is reestablished, which is attributed to the formation of [Formula: see text] complexes with the anions. It thus turns out from RR spectroscopic evidence that the retinyl chromophore in BR is largely governed by the [Formula: see text] ion-pair formation, which is stabilized by surrounding water molecules.

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“…[33][34][35] In contrast, however, resonance Raman data 25,36,37 and recent double-quantum solid-state NMR experiments 32 converge toward single-bond character for C14-C15, suggesting that the polaronic charge defect might hop over the vicinity of the Schiff base, settling in the middle of the polyene chain next to C12. 32 An objective of recent DFT QM/MM studies has been to resolve such a contradictory picture by providing a detailed first principles description of the electronic density of the chromophore as influenced by the protein environment.…”

Section: Charge Distributionmentioning

confidence: 90%

Computational Studies of the Primary Phototransduction Event in Visual Rhodopsin

2006

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This Account addresses recent advances in the elucidation of the detailed molecular rearrangements due to the primary photochemical event in rhodopsin, a prototypical G-protein-coupled receptor (GPCR) responsible for the signal transmission cascade in the vertebrate vision process. The reviewed studies provide fundamental insight on long-standing problems regarding the assembly and function of the individual residues and bound water molecules that form the rhodopsin active site, a center that catalyzes the 11-cis/all-trans isomerization of the retinyl chromophore in the primary step of the phototransduction mechanism. Emphasis is placed on the authors' recent computational studies, based on state-of-the-art quantum mechanics/molecular mechanics (QM/MM) hybrid methods, addressing the structural refinement of the retinyl chromophore binding site in high-resolution X-ray structures of bovine visual rhodopsin, the energy storage mechanism, and the molecular origin of spectroscopic changes due to the primary photochemical event.

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Assignment and interpretation of hydrogen out-of-plane vibrations in the resonance Raman spectra of rhodopsin and bathorhodopsin

Cited by 212 publications

References 20 publications

Photoisomerization mechanism of the rhodopsin chromophore: picosecond photolysis of pigment containing 11-cis-locked eight-membered ring retinal.

Photoisomerization mechanism of the rhodopsin chromophore: picosecond photolysis of pigment containing 11-cis-locked eight-membered ring retinal.

Structure of bacteriorhodopsin in the acidified membrane and at high ionic strength: resonance Raman study

Computational Studies of the Primary Phototransduction Event in Visual Rhodopsin

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