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Two bacteriorhodopsin M intermediates differing in accesibility of the Schiff base for azide
Author(s) -
Radionov Alexey N.,
Kaulen Andrey D.
Publication year - 1996
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 - 10.1016/0014-5793(96)00476-0
Subject(s) - azide , bacteriorhodopsin , chemistry , schiff base , glutaraldehyde , stereochemistry , photochemistry , medicinal chemistry , biochemistry , organic chemistry , membrane
Glutaraldehyde treatment leads to the inhibition (i) of the M intermediate decay in wild‐type bacteriorhodopsin (bR) and (ii) of the azide‐facilitated M decay in the D96N mutant bR. LuCl 3 is shown to be a more potent inhibitor of both processes. Glycerol and sucrose are also inhibitors. None of these agents change the linearity of the azide concentration dependency of the M decay in the D96N mutant but they do shift this dependency to higher azide concentrations. It is concluded that the two M forms are in equilibrium. These M forms differ in the accessibility of the Schiff base for azide and, probably, also for water molecules. The above‐mentioned agents shift the equilibrium toward the less accessible M form. The data obtained are in line with the model of azide action as the penetrating proton donor and can hardly be realized within the framework of the model of Le Coutre et al. [(1995) Proc. Natl. Acad. Sci. USA 92, 4962–4966] which assumes that a bound anionic form of azide catalyzes proton transfer to the Schiff base.