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Complicated character of the M decay pH dependence in the D96N mutant is due to the two pathways of the M conversion
Author(s) -
Radionov Alexey N.,
Kalaidzidis Inna V.,
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/s0014-5793(96)01334-8
Subject(s) - chemistry , bacteriorhodopsin , proton , mutant , biophysics , proton transport , kinetics , ion , azide , halobacteriaceae , crystallography , biochemistry , halobacterium salinarum , membrane , physics , organic chemistry , quantum mechanics , biology , gene
At high ionic strength, the pH dependence of the M intermediate decay in a photocycle of the D96N mutant bacteriorhodopsin shows a complicated behavior which is found to be due to the coexistence of two pathways of the M conversion. The M decay which dominates at pH <5 is coupled to the proton uptake from the cytoplasmic surface and proceeds probably through the N intermediate. This pathway is inhibited by glutaraldehyde, the potent inhibitor of M decay in the wildtype bacteriorhodopsin and of the azide‐facilitated M decay in the D96N mutant. Another pathway of the M decay is predominant at pH > 5. This pathway is insensitive to glutaraldehyde and some other similar inhibitors (lutetium ions, sucrose and glycerol). On the other hand, it is sensitive to the pK changes of the group X (Glu‐204) in the outward proton pathway. Possibly, the M decay through this pathway represents a reverse H + transport process (the proton uptake from the external surface) and proceeds via the L intermediate.