Vibrational analysis of the all-trans-retinal chromophore in light-adapted bacteriorhodopsin

Smith, Steven O.; Braiman, Mark S.; Myers, Anne B.; Pardoen, J. A.; Courtin, J. M. L.; Winkel, C.; Lugtenburg, J.; Mathies, Richard A.

doi:10.1021/ja00244a038

Cited by 261 publications

(568 citation statements)

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“…Nearly all of the bands observed at wavenumber shifts above 700 cm -~ were observed in the resonance Raman spectrum of bR excited at 514.5 nm and have been assigned by Mathies and co-workers. 16 A strong contribution from the polypeptide chain or membrane fragments themselves is conspicuously absent, although the broad shoulder at ~ 1650 cm -1 may be scattering by amide I vibrations of the polypeptide backbone.…”

Section: Resultsmentioning

confidence: 99%

Fourier Transform Raman Spectroscopy of Photoactive Proteins with Near-Infrared Excitation

Johnson

Rubinovitz

1990

Appl Spectrosc

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The Fourier transform (FT) Raman spectroscopic treatment of the photoactive proteins bacteriorhodopsin and the photosynthetic reaction center is reported, with excitation at 1.06/~m. Excitation at this wavelength circumvents the limitations on resonance Raman spectroscopy of these proteins imposed by their photolability and by the fluorescence of free pigments or impurities. The spectra are dominated by nonresonant Raman scattering by the protein-bound pigments retinal (in bacteriorhodopsin) and bacteriopheophytin, bacteriochlorophyll, and carotenoids (in reaction centers). The relative intensities of retinylidene modes in the spectrum for nonresonant FT Raman spectroscopy of bacteriorhodopsin are nearly identical to those observed in the resonance Raman spectrum of bacteriorhodopsin.

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Section: Resultsmentioning

confidence: 99%

Fourier Transform Raman Spectroscopy of Photoactive Proteins with Near-Infrared Excitation

Johnson

Rubinovitz

1990

Appl Spectrosc

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“…Resonance Raman spectra of BR568 were obtained by a rapid-flow technique (11), and spectra of L550 were obtained by a dual-beam rapid-flow system (8). The n-butylamine PSB of all-trans- [14,15-2H]retinal was prepared as the microcrystalline precipitate of the chloride salt (15).…”

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confidence: 99%

“…In all calculations, the chromophore was truncated by replacing carbons 1, 4, and 18 of the ionone ring and the 8 carbon of lysine with alkyl groups, which have a mass of 15 and the default parameters of an sp3 carbon. The FG calculations for the all-trans configuration used the force field and geometry for BR56, (11). The nearly planar geometry of the 13-cis configuration was generated by using QCFF.…”

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confidence: 99%

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Bacteriorhodopsin's L550 intermediate contains a C14-C15 s-trans-retinal chromophore.

Fodor

Pollard

Gebhard

et al. 1988

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

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Conformational changes of the retinal chromophore about the C14-C15 bond in bacteriorhodopsin (BR) have been proposed in models for the mechanism of light-driven proton transport. To determine the C14-C15 conformation in BR's Lsso intermediate, we have examined the resonance Raman spectra of BR derivatives regenerated with retinal deuterated at the 14 and 15 positions. Vibrational calculations show that the C14-2H and C15-2H rocking modes form symmetric (A) and antisymmetric (B) combinations in [14,15_2H]retinal chromophores. When there is a trans conformation about the single bond between C14 and C15 (14-s-trans), a small frequency separation or splitting is observed between the A and B modes, which are found at =970 cm-'. In 14-s-cis molecules, the splitting is large, and the Raman-active symmetric A mode is predicted at =850 cm -1.In addition, the monodeuterium rock should appear at an unusually low frequency (920 -930 cm ')in the 14-2H-labeled 14-s-cis molecules. These patterns are insensitive to computa- L5sO contains a 14-s-trans chromophore and suggest that only 14-s-trans structures are involved in the proton pumping photocycle of BR.Bacteriorhodopsin (BR) is an intrinsic membrane protein that functions as a light-driven proton pump in the bacterium Halobacterium halobium (1). The photocycle of BR begins with the photochemical all-trans-to-13-cis isomerization ofthe retinal prosthetic group in the parent pigment BR5.. The pigment then decays through the K and L550 intermediates, and the Schiff base nitrogen deprotonates producing M412. A number of models have been proposed to explain how isomerization and Schiff-base deprotonation are coupled to proton transport. Isomerization-driven charge separation is one widely accepted idea (2-4), and models involving a cis conformation at the single bond between C14 and C15 (14-s-cis) for the K and L550 intermediates have been proposed by Schulten and Tavan (5) and by Liu et al. (6).Vibrational spectroscopy has been the primary tool for determining the structure of the retinal chromophore in BR's early photointermediates (7). In a recent study, Smith et al. (8) examined the conformation of the C14-C15 bond in K and L550 by recognizing that one characteristic of an s-cis bond is the -100 cm -1 lowering of the C14-C15 stretching mode. The C14-C15 mode in L550 was assigned at ==1172 cm-1, close to the 1155 cm-1 value observed in later Fourier transform infrared studies (9). The absence of any large frequency-lowering of this mode compared with the 13-cis protonated Schiff base (PSB) suggested that the chromophore was 14-s-trans. Subsequent MNDO (modified neglect of differential overlap) calculations by Tavan and Schulten (10) confirmed the lowering of the C14-C15 stretching mode in s-cis conformers; however, they argued that by displacing the Schiff base counterion they could enhance the tr-electron delocalization sufficiently to counteract the geometric effect of s-cis isomerization. While there is no direct support for their assumed counterion distances, ...

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“…The results from the research described above on BR as well as a variety of other spectroscopic studies [7,10,39,63,82,108,139,161,162,225]) led by 1990 to the "standard" model of the BR proton pump mechanism" shown in Fig. 13.…”

Section: Early Model Of the Br Proton Pump Mechanismmentioning

confidence: 97%

The early development and application of FTIR difference spectroscopy to membrane proteins: A personal perspective

Rothschild

2016

BSI

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Abstract. Membrane proteins facilitate some of the most important cellular processes including energy conversion, ion transport and signal transduction. While conventional infrared absorption provides information about membrane protein secondary structure, a major challenge is to develop a dynamic picture of the functioning of membrane proteins at the molecular level. The introduction of FTIR difference spectroscopy around 1980 to study structural changes in membrane proteins along with a number of associated techniques including protein isotope labeling, site-directed mutagenesis, polarization dichroism, attenuated total reflection and time-resolved spectroscopy have led to significant progress towards this goal. It is now possible to routinely detect conformational changes of individual amino acid residues, backbone peptides, binding ligands, chromophores and even internal water molecules under physiological conditions with time-resolution down to nanoseconds. The advent of ultrafast pulsed-IR lasers has pushed this time-resolution down to femtoseconds. The early development of FTIR difference spectroscopy as applied to membrane proteins with special focus on bacteriorhodopsin is reviewed from a personal perspective.

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Vibrational analysis of the all-trans-retinal chromophore in light-adapted bacteriorhodopsin

Cited by 261 publications

References 3 publications

Fourier Transform Raman Spectroscopy of Photoactive Proteins with Near-Infrared Excitation

Fourier Transform Raman Spectroscopy of Photoactive Proteins with Near-Infrared Excitation

Bacteriorhodopsin's L550 intermediate contains a C14-C15 s-trans-retinal chromophore.

The early development and application of FTIR difference spectroscopy to membrane proteins: A personal perspective

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