Bacteriorhodopsin “detergent-monomers,” blue shift and velocity of light-dark adaptation

Massotte, Dominique; Aghion, Jacques

doi:10.1016/0006-291x(91)92080-4

Cited by 12 publications

(7 citation statements)

References 12 publications

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“…The population ratio is modified by changes in temperature, pH, amino acid sequence of bR (Song et al, 1995), and pressure . The retinal isomer ratio has also been determined on membranes treated with Triton X-100, a detergent that produces monomers of bR (Massote and Aghion, 1991), giving a population of 71% of bR 548 at 277 K (Scherrer et al, 1989). The relative populations of the two forms in the dark-adapted bR suggest that the difference in their free energies is Յk B T (where k B is the Boltzmann constant and T is the temperature).…”

Section: Introductionmentioning

confidence: 99%

Simulation Analysis of the Retinal Conformational Equilibrium in Dark-Adapted Bacteriorhodopsin

Baudry

Crouzy

Roux

et al. 1999

Biophysical Journal

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In dark-adapted bacteriorhodopsin (bR) the retinal moiety populates two conformers: all-trans and (13,15)cis. Here we examine factors influencing the thermodynamic equilibrium and conformational transition between the two forms, using molecular mechanics and dynamics calculations. Adiabatic potential energy mapping indicates that whereas the twofold intrinsic torsional potentials of the C13==C14 and C15==N16 double bonds favor a sequential torsional pathway, the protein environment favors a concerted, bicycle-pedal mechanism. Which of these two pathways will actually occur in bR depends on the as yet unknown relative weight of the intrinsic and environmental effects. The free energy difference between the conformers was computed for wild-type and modified bR, using molecular dynamics simulation. In the wild-type protein the free energy of the (13,15)cis retinal form is calculated to be 1.1 kcal/mol lower than the all-trans retinal form, a value within approximately kBT of experiment. In contrast, in isolated retinal the free energy of the all-trans state is calculated to be 2.1 kcal/mol lower than (13,15)cis. The free energy differences are similar to the adiabatic potential energy differences in the various systems examined, consistent with an essentially enthalpic origin. The stabilization of the (13,15)cis form in bR relative to the isolated retinal molecule is found to originate from improved protein-protein interactions. Removing internal water molecules near the Schiff base strongly stabilizes the (13,15)cis form, whereas a double mutation that removes negative charges in the retinal pocket (Asp85 to Ala; Asp212 to Ala) has the opposite effect.

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Section: Introductionmentioning

confidence: 99%

Simulation Analysis of the Retinal Conformational Equilibrium in Dark-Adapted Bacteriorhodopsin

Baudry

Crouzy

Roux

et al. 1999

Biophysical Journal

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“…The CD spectrum of native BR in purple membrane in the region of the absorption band consists of two bands of opposite signs and different amplitudes, viz., a positive band at 535 nm and a much weaker negative band at 600 nm. This biphasic spectrum is observed only for the intact purple membrane; when the membrane is solubilized, e.g., by treatment with detergents, the CD spectrum becomes monophasic positive and matches the UV/vis spectrum (22,23). According to one line of reasoning, electronic interaction of the retinal chromophores in the ordered purple membrane gives rise to delocalized exciton states and the typical split CD spectrum.…”

Section: Resultsmentioning

confidence: 89%

The Chromophore Induces a Correct Folding of the Polypeptide Chain of Bacteriorhodopsin

et al. 1998

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The pK values of the Schiff bases of several bacteriorhodopsin (BR) preparations have been determined by titration. While for the native protein a high pK of 13 has been reported [Druckmann et al. (1982) Biochemistry 21, 4953], we find that a BR reconstituted from retinal and the apoprotein obtained from the retinal-deficient strain JW5 exhibits a low pK value, 8.5. When the retinal chromophore is added to growing JW5 cells leading to in vivo BR formation, this BR shows a high Schiff base pK, >/=10.2. A value of 9.3 was determined when BR was reconstituted from retinal and BO, obtained from bleaching BR with hydroxylamine. A low pK value of 8.1 was found when 13-trifluoro(CF3)-retinal was used as chromophore for in vitro reconstitution [Sheves et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 3262], which is confirmed in this study. When we add CF3-retinal to growing JW5 cells, this low pK shifts to 9.1. Besides wild-type protein, the apoprotein from the mutant D96N (from the chromophore-deficient strain L-07) was also used for in vitro reconstitution with either chromophore, retinal or CF3-retinal. Irrespective of the chromophore used, both mutant BRs exhibit low pK values of their Schiff bases of 8.1. Flash photolysis with respect to the rise and decay of the M-photocycle intermediate of wild-type and D96N-mutated BR carrying retinal and CF3-retinal revealed that in both proteins the incorporation of the trifluororetinal leads to a faster rise of the M-intermediate and to a slower decay. Since the apoprotein from the chromophore-deficient JW5 strain of H. salinarium, despite its lower boyant density, is arranged into trimers (according to CD measurements), we propose that the high pK value of the BR Schiff base is induced by long-distance interactions between BR molecules in the purple membrane patches which control the pK of the chromophore.

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“…The highest concentrations of CTAB, SDS and C6E2 utilized in these experiments are 64 μ m , 1.28 m m and 25 m m , respectively. All of these are below the respective critical micelle concentrations (CMC) of 0.9 m m (41), 7.1 m m (42) and 144 m m (43). The micelle effect will play a minor role in the following observations of steady‐state absorption and circular dichroism spectra and in the dynamics of the O intermediate in the photocycle.…”

Section: Resultsmentioning

confidence: 96%

“…London and Khorana showed that bR undergoes denaturation with partial loss of the secondary structure and loss of retinal binding ability upon treatment with SDS (47). In addition, the retinal can be bleached by the approach of the negatively charged hydrophilic SDS head to the Schiff-base linkage of the retinal (42). At low SDS concentrations, the drop in the A 280nm ⁄ A 568nm ratio can be attributed to SDS attachment on the bR surface due to nonpolar interaction between the hydrocarbon tails of SDS and the hydrophobic surface of the bR.…”

Section: Effect Of Chemical Environment On the Uv-vis And CD Spectra mentioning

confidence: 99%

Bacteriorhodopsin O‐state Photocycle Kinetics: A Surfactant Study

Chu

El‐Sayed

2010

Photochem & Photobiology

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The spectroscopy and dynamics of interaction between the O intermediate of bacteriorhodopsin (bR) and several surfactants (cetrimonium bromide [CTAB], sodium dodecyl sulfate [SDS] and diethylene glycol mono-n-hexyl ether [C6E2]) were investigated using steady-state UV-VIS spectrometry, circular dichroism spectroscopy and time-resolved absorption techniques. The steady-state spectral results show that bR can retain its trimeric state without severe damage in the molar concentration ratio of C6E2/bR ranging up to 4000. Time-resolved observations indicate that the rise and decay rates and transient populations of the O state can be increased in the presence of nonionic surfactant C6E2; however, these studies indicate the opposite phenomenon in the presence of the ionic surfactants CTAB and SDS. The observed 40% enhancement in the transient population of the O intermediate state that results from treatment of C6E2 is proposed to result from an expanding bR structure, which leads to more effective proton pumping efficiency in the photosynthetic system of bR.

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Bacteriorhodopsin “detergent-monomers,” blue shift and velocity of light-dark adaptation

Cited by 12 publications

References 12 publications

Simulation Analysis of the Retinal Conformational Equilibrium in Dark-Adapted Bacteriorhodopsin

Simulation Analysis of the Retinal Conformational Equilibrium in Dark-Adapted Bacteriorhodopsin

The Chromophore Induces a Correct Folding of the Polypeptide Chain of Bacteriorhodopsin

Bacteriorhodopsin O‐state Photocycle Kinetics: A Surfactant Study

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