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P 588 , A SECOND RETINAL‐CONTAINING PIGMENT IN HALOBACTERIUM HALOBIUM
Author(s) -
Weber H. J.,
Bogomolni R. A.
Publication year - 1981
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.1751-1097.1981.tb05465.x
Subject(s) - bacteriorhodopsin , proton , action spectrum , electrochemical gradient , pigment , retinal , biophysics , halobacterium salinarum , chemistry , mutant , photochemistry , vesicle , photoprotein , biochemistry , membrane , biology , bioluminescence , physics , organic chemistry , quantum mechanics , gene
— Halobacterium mutant strains with defects in the biosynthesis of various pigments have been isolated. One of these strains, mutant ET‐15, is incapable of producing the light‐driven proton pump bacteriorhodopsin and the carotenoid bacterioruberin. However, ET‐15 synthesizes another photochemically active, retinal‐containing pigment, P 588 , which mediates light‐induced proton uptake enhanced by uncouplers. P 588 and bacteriorhodopsin are simultaneously present in wild‐type cells grown under normal conditions; however, they can be distinguished by the following criteria.1 They can be separated by independent mutational events. 2 Proton ionophores such as FCCP diminish bacteriorhodopsin‐driven proton translocation but enhance P 588 ‐mediated proton flows. We define here proton translocations which can be diminished by the addition of uncouplers (e.g. FCCP) as ‘active’, others which can be enhanced by FCCP as ‘passive’. 3 The kinetic and spectral properties of the photocycle intermediates of bacteriorhodopsin and P 588 are different. 4 The action spectrum for photocycling of P 588 is red‐shifted with respect to that for bacteriorhodopsin.A comparison of action spectra for proton translocations with that for photocycling links pigment P 588 and light‐driven, passive proton uptake by ET‐15 envelope vesicles. When chemically bleached P 588 was regenerated with all‐ trans ‐retinal, both photochemical activity and light‐induced proton inflow were restored to equal extents. This identifies P 588 with the energizer for the passive proton flows.