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Cl − ‐dependent photovoltage responses of bacteriorhodopsin: comparison of the D85T and D85S mutants and wild‐type acid purple form
Author(s) -
Kalaidzidis Inna V,
Kaulen Andrey D
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)01390-2
Subject(s) - bacteriorhodopsin , mutant , chemistry , wild type , photoprotein , surface photovoltage , photochemistry , biochemistry , physics , bioluminescence , spectroscopy , membrane , gene , quantum mechanics
Laser flash‐induced photovoltage responses of the D85S and D85T mutants as well as of the wild‐type acid blue form are similar and reflect intraprotein charge redistribution caused by retinal isomerization. The Cl − ‐induced transition of all of these blue forms into purple ones is accompanied by the appearance of electrogenic stages, which is probably associated with Cl − translocation in the cytoplasmic direction. Cl − translocation efficiency of these purple forms is much lower than that of the proton transport by the wild‐type bacteriorhodopsin. The values of the efficiency do not exceed 15, 8 and 3% for the D85T, D85S and wild‐type acid purple form, respectively. Cl − induces an additional electrogenic phase in the photovoltage responses of the D85S mutant and the wild‐type acid purple form. This phase is supposed to be associated with the reversible Cl − movement in the extracellular direction. It is interesting that this component is absent in the photovoltage response of the D85T mutant which has, like halorhodopsin, a threonine residue at position 85.