Light scattering changes and protein distortion in the bacteriorhodopsin during the photocycle

Czégé, József

doi:10.1016/0014-5793(88)80991-8

Cited by 11 publications

(4 citation statements)

References 12 publications

(14 reference statements)

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“…According to the structure data of the intermediates the motions in PRG seem to be small. However, large bending of pm associated with the photocycle was found by two methods: light scattering (11)(12)(13) and electrooptics (14). The time-resolved light scattering data show that the bending appears already during M formation (11)(12)(13), whereas the published electrooptical measurements that deal with pm containing the mutant BR D96N assign it in general to the M intermediate resolving only its decay.…”

Section: Discussionmentioning

confidence: 99%

“…However, large bending of pm associated with the photocycle was found by two methods: light scattering (11)(12)(13) and electrooptics (14). The time-resolved light scattering data show that the bending appears already during M formation (11)(12)(13), whereas the published electrooptical measurements that deal with pm containing the mutant BR D96N assign it in general to the M intermediate resolving only its decay. Careful analysis of light scattering data (11)(12)(13) indicates that the pm at pH.5 (as in our case) bends toward the extracellular side suggesting that PRGs in triplet come somewhat nearer to each other.…”

Section: Discussionmentioning

confidence: 99%

“…An explanation, based on intermolecular interaction between the proton release groups (PRG defined in Balashov et al (8)) of BR trimers, is presented. Rather small structural changes in PRG during the transition from ground state BR to M intermediate were found by x-ray diffraction (9,10) though large bending of pm was reported and assigned to M formation (11)(12)(13)(14). We hypothesize that the changes are due to electrical interaction in the triplet supported by bending.…”

Section: Introductionmentioning

confidence: 93%

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Actinic Light-Energy Dependence of Proton Release from Bacteriorhodopsin

Tóth-Boconádi

Taneva

Keszthelyi

2005

Biophysical Journal

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Measuring the light-density (fluence) dependence of proton release from flash excited bacteriorhodopsin with two independent methods we found that the lifetime of proton release increases and the proton pumping activity, defined as a number of protons per number of photocycle, decreases with increasing fluence. An interpretation of these results, based on bending of purple membrane and electrical interaction among the proton release groups of bacteriorhodopsin trimer, is presented.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 93%

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Actinic Light-Energy Dependence of Proton Release from Bacteriorhodopsin

Tóth-Boconádi

Taneva

Keszthelyi

2005

Biophysical Journal

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“…As a possible origin of such a decrease, transient changes in the curvature of the membranes could be considered. However, light-scattering experiments have shown that in the gel the membrane is unable to change its curvature (i.e., bending processes associated with the bR photocycle in solution are absent − ). The possibility of significant transient changes of S 2 in our experiments is thus excluded.…”

Section: Discussionmentioning

confidence: 99%

Time-Resolved Linear Dichroism and Linear Birefringence of Bacteriorhodopsin at Alkaline pH: Identification of Two N Substates with Different Orientations of the Transition Dipole Moment

2004

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Transient linear dichroism and linear birefringence changes in the photocycle of bacteriorhodopsin at alkaline pH were measured with magnetically oriented purple membrane samples using the method of isotropic excitation (Borucki, B.; Otto, H.; Heyn, M. P. J. Phys. Chem. B 1999, 103, 6371−6383). At pH 10.4, the accumulation of the O intermediate is negligible, and N is the only intermediate that is relevant in the M decay and the recovery of the bR ground state. We introduced a new analytical approach that is model-independent and makes use of the transient linear dichroism in combination with isotropic absorbance changes. SVD analysis reveals that only one species (spectral component), namely, the N intermediate, is involved in the M decay at pH 10.4. The spectrum of this intermediate and its average anisotropy are determined from an eigenvalue equation. The transient linear dichroism data suggest a transition between two substates of the N intermediate with different anisotropies (i.e., with different orientations of the electronic transition dipole moment). Assuming that the polar angle of the transition dipole moment with respect to the membrane normal is 70° in the bR ground state, we get 66.3° (upper limit) for the first and 67.9° (lower limit) for the second N substate. The reorientation of the chromophore in the N1 → N2 transition is probably associated with the movement of the protonated Schiff base away from Asp96, suggesting that it serves as a reprotonation switch for Asp96 by stabilizing the protonation state of the Schiff base. In contrast to measurements at neutral pH, the linear birefringence changes at alkaline pH contain a wavelength-independent component that is not due to the transient absorption changes and whose time dependence is correlated with the kinetics of the N intermediate. This result is attributed to an electro-optical effect caused by the large electric field generated by the transient negative charge on Asp96 in the N intermediate. Alternatively this change in Δn may be due to the major conformational change in the cytoplasmic region of the membrane during N.

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Two bacteriorhodopsin M intermediates differing in accesibility of the Schiff base for azide

Radionov

Kaulen

1996

FEBS Letters

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Key words: Bacteriorhodopsin; Photocycle; Proton transport; Azide; Purple membrane; D96N mutant; Halobacterium salinarium pies. It should be stressed that the inhibitory mechanisms of the above agents are probably quite different, i.e. arrest of the conformational changes in the case of glutaraldehyde or LuC13 [23,24] and a decrease in the water activity in the case of glycerol and sucrose [20]. The data obtained are in line with the model of azide action as the penetrating proton donor. They revealed two M forms differing in the accessibility of the Schiff base for azide and, possibly, water molecules. Material and methodsAll the experiments were carried out using freshly prepared purple membrane sheets from the halobacterial wild-type ET1001 and mutant strain D96N. The latter was kindly donated by Prof. D. Oesterbelt (Max-Planck Institut fiir Biochimie, Germany).The measurement were performed on light-adapted purple membrane suspensions at 20°C. The bR photocycle was monitored using a single-beam spectrophotometer [7,19,24]. Photoexcitation of bR was carried out with a YG-481 Quantel neodymium laser (~. = 532 nm; pulse half-width, 15 ns; energy, 10 mJ).Maximal glutaraldehyde inhibition of the bR photocycle was achieved by treatment of purple membranes in 1% glutaraldehyde overnight at 20°C in 5 mM Na-citrate-phosphate-Tris buffer at pH 8.

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Light scattering changes and protein distortion in the bacteriorhodopsin during the photocycle

Cited by 11 publications

References 12 publications

Actinic Light-Energy Dependence of Proton Release from Bacteriorhodopsin

Actinic Light-Energy Dependence of Proton Release from Bacteriorhodopsin

Time-Resolved Linear Dichroism and Linear Birefringence of Bacteriorhodopsin at Alkaline pH: Identification of Two N Substates with Different Orientations of the Transition Dipole Moment

Two bacteriorhodopsin M intermediates differing in accesibility of the Schiff base for azide

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