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THE INWARD H + PATHWAY IN BACTERIORHODOPSIN: THE ROLE OF M 412 AND P(N) 560 INTERMEDIATES*
Author(s) -
Danshina S. V.,
Drachev L. A.,
Kaulen A. D.,
Skulachev V. P.
Publication year - 1992
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1992.tb08518.x
Subject(s) - bacteriorhodopsin , chemistry , halobacteriaceae , kinetics , light intensity , crystallography , monomer , molecule , halobacterium , photoprotein , analytical chemistry (journal) , halobacterium salinarum , membrane , optics , chromatography , physics , biochemistry , organic chemistry , quantum mechanics , polymer , bioluminescence
— In purple bacteriorhodopsin sheets adsorbed onto the phospholipid‐impregnated collodion film, electrogenic stages are identified correlating with decays of the M and N(P)‐type intermediates. It is concluded that both M → N and N → bR transitions are electrogenic. The M decay is shown to be of a complex kinetics. In purple sheets, the lower the light intensity, the higher the rate of “slow M” decay. Such a dependence, which is absent from monomeric bacteriorhodopsin in proteoliposomes and from Triton X‐100‐solubilized protein, may be explained by the inhibiting effect of a light‐induced conformation change in a bacteriorhodopsin molecule upon the M decay in some other bacteriorhodopsin molecules within the same sheet. The light intensity‐independent “slow M” decay in solubilized bacteriorhodopsin is shown to correlate with the decay of the N intermediate and H + uptake after the flash. In contrast to “fast M”, “slow M” is pH dependent, closely resembling in this respect the N intermediate. It is suggested that there is a fast light‐independent equilibration between M and N so that “slow M” represents the portion of the M pool that monitors the N concentration. The M → N equilibrium is assumed to be involved in the effect of the light‐induced electric field on the M decay. No direct effect of light on the equilibrium was found.