Photoreactions of bacteriorhodopsin at acid pH

G. Váró, J. K. Lanyi

Research output: Contribution to journalArticle

75 Citations (Scopus)

Abstract

It has been known that bacteriorhodopsin, the retinal protein in purple membrane which functions as a light-driven proton pump, undergoes reversible spectroscopic changes at acid pH. The absorption spectra of various bacteriorhodopsin species were estimated from measured spectra of the mixtures that form at low pH, in the presence of sulfate and chloride. The dependency of these on pH and the concentration of Cl- fit a model in which progressive protonation of purple membrane produces 'blue membrane', which will bind, with increasing affinity as the pH is lowered, chloride ions to produce 'acid purple membrane'. Transient spectroscopy with a multichannel analyzer identified the intermediates of the photocycles of these altered pigments, and described their kinetics. Blue membrane produced red-shifted KL-like and L-like products, but no other photointermediates, consistent with earlier suggestions. Unlike others, however, we found that acid purple membrane exhibited a very different photocycle: its first detected intermediate was not like KL in that it was much more red-shifted, and the only other intermediate detectable resembled the O species of the bacteriorhodopsin photocycle. An M-like intermediate, with a deprotonated Schiff base, was not found in either of these photocycles. There are remarkable similarities between the photoreactions of the acid forms of bacteriorhodopsin and the chloride transport system halorhodopsin, where the Schiff base deprotonation seems to be prevented by lack of suitable aspartate residues, rather than by low pH.

Original languageEnglish
Pages (from-to)1143-1151
Number of pages9
JournalBiophysical Journal
Volume56
Issue number6
Publication statusPublished - 1989

Fingerprint

Bacteriorhodopsins
Purple Membrane
Acids
Chlorides
Schiff Bases
Halorhodopsins
Proton Pumps
Membranes
Aspartic Acid
Sulfates
Spectrum Analysis
Ions
Light
Proteins

ASJC Scopus subject areas

  • Biophysics

Cite this

Photoreactions of bacteriorhodopsin at acid pH. / Váró, G.; Lanyi, J. K.

In: Biophysical Journal, Vol. 56, No. 6, 1989, p. 1143-1151.

Research output: Contribution to journalArticle

Váró, G & Lanyi, JK 1989, 'Photoreactions of bacteriorhodopsin at acid pH', Biophysical Journal, vol. 56, no. 6, pp. 1143-1151.
Váró, G. ; Lanyi, J. K. / Photoreactions of bacteriorhodopsin at acid pH. In: Biophysical Journal. 1989 ; Vol. 56, No. 6. pp. 1143-1151.
@article{9b1f8567a8c545fd8dcfcab892223306,
title = "Photoreactions of bacteriorhodopsin at acid pH",
abstract = "It has been known that bacteriorhodopsin, the retinal protein in purple membrane which functions as a light-driven proton pump, undergoes reversible spectroscopic changes at acid pH. The absorption spectra of various bacteriorhodopsin species were estimated from measured spectra of the mixtures that form at low pH, in the presence of sulfate and chloride. The dependency of these on pH and the concentration of Cl- fit a model in which progressive protonation of purple membrane produces 'blue membrane', which will bind, with increasing affinity as the pH is lowered, chloride ions to produce 'acid purple membrane'. Transient spectroscopy with a multichannel analyzer identified the intermediates of the photocycles of these altered pigments, and described their kinetics. Blue membrane produced red-shifted KL-like and L-like products, but no other photointermediates, consistent with earlier suggestions. Unlike others, however, we found that acid purple membrane exhibited a very different photocycle: its first detected intermediate was not like KL in that it was much more red-shifted, and the only other intermediate detectable resembled the O species of the bacteriorhodopsin photocycle. An M-like intermediate, with a deprotonated Schiff base, was not found in either of these photocycles. There are remarkable similarities between the photoreactions of the acid forms of bacteriorhodopsin and the chloride transport system halorhodopsin, where the Schiff base deprotonation seems to be prevented by lack of suitable aspartate residues, rather than by low pH.",
author = "G. V{\'a}r{\'o} and Lanyi, {J. K.}",
year = "1989",
language = "English",
volume = "56",
pages = "1143--1151",
journal = "Biophysical Journal",
issn = "0006-3495",
publisher = "Biophysical Society",
number = "6",

}

TY - JOUR

T1 - Photoreactions of bacteriorhodopsin at acid pH

AU - Váró, G.

AU - Lanyi, J. K.

PY - 1989

Y1 - 1989

N2 - It has been known that bacteriorhodopsin, the retinal protein in purple membrane which functions as a light-driven proton pump, undergoes reversible spectroscopic changes at acid pH. The absorption spectra of various bacteriorhodopsin species were estimated from measured spectra of the mixtures that form at low pH, in the presence of sulfate and chloride. The dependency of these on pH and the concentration of Cl- fit a model in which progressive protonation of purple membrane produces 'blue membrane', which will bind, with increasing affinity as the pH is lowered, chloride ions to produce 'acid purple membrane'. Transient spectroscopy with a multichannel analyzer identified the intermediates of the photocycles of these altered pigments, and described their kinetics. Blue membrane produced red-shifted KL-like and L-like products, but no other photointermediates, consistent with earlier suggestions. Unlike others, however, we found that acid purple membrane exhibited a very different photocycle: its first detected intermediate was not like KL in that it was much more red-shifted, and the only other intermediate detectable resembled the O species of the bacteriorhodopsin photocycle. An M-like intermediate, with a deprotonated Schiff base, was not found in either of these photocycles. There are remarkable similarities between the photoreactions of the acid forms of bacteriorhodopsin and the chloride transport system halorhodopsin, where the Schiff base deprotonation seems to be prevented by lack of suitable aspartate residues, rather than by low pH.

AB - It has been known that bacteriorhodopsin, the retinal protein in purple membrane which functions as a light-driven proton pump, undergoes reversible spectroscopic changes at acid pH. The absorption spectra of various bacteriorhodopsin species were estimated from measured spectra of the mixtures that form at low pH, in the presence of sulfate and chloride. The dependency of these on pH and the concentration of Cl- fit a model in which progressive protonation of purple membrane produces 'blue membrane', which will bind, with increasing affinity as the pH is lowered, chloride ions to produce 'acid purple membrane'. Transient spectroscopy with a multichannel analyzer identified the intermediates of the photocycles of these altered pigments, and described their kinetics. Blue membrane produced red-shifted KL-like and L-like products, but no other photointermediates, consistent with earlier suggestions. Unlike others, however, we found that acid purple membrane exhibited a very different photocycle: its first detected intermediate was not like KL in that it was much more red-shifted, and the only other intermediate detectable resembled the O species of the bacteriorhodopsin photocycle. An M-like intermediate, with a deprotonated Schiff base, was not found in either of these photocycles. There are remarkable similarities between the photoreactions of the acid forms of bacteriorhodopsin and the chloride transport system halorhodopsin, where the Schiff base deprotonation seems to be prevented by lack of suitable aspartate residues, rather than by low pH.

UR - http://www.scopus.com/inward/record.url?scp=0024829218&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0024829218&partnerID=8YFLogxK

M3 - Article

VL - 56

SP - 1143

EP - 1151

JO - Biophysical Journal

JF - Biophysical Journal

SN - 0006-3495

IS - 6

ER -