Photochemistry of two rhodopsinlike pigments in bacteriorhodopsin-free mutant of Halobacterium halobium

Two photocycles due to two different pigments were found in membrane vesicles of a bacteriorhodopsin-free mutant of Halobacterium halobium. A pigment absorbing approximately 590 nm halorhodopsin (HR) underwent a faster photocycle with a phototransient at approximately 490 nm (half-time of decay, tau...

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Bibliographic Details
Published in:Biophysical journal 1983-10, Vol.44 (1), p.59-64
Main Authors: Hazemoto, N., Kamo, N., Terayama, Y., Kobatake, Y., Tsuda, M.
Format: Article
Language:English
Subjects:
bacteriorhodopsin
Bacteriorhodopsins - metabolism
Carotenoids - metabolism
deficient mutant
Halobacterium - metabolism
Halobacterium halobium
Halorhodopsins
Hydrogen-Ion Concentration
Kinetics
Mathematics
Photochemistry
pigments
Retinal Pigments
Rhodopsin
Structure-Activity Relationship
Thermodynamics
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Summary:Two photocycles due to two different pigments were found in membrane vesicles of a bacteriorhodopsin-free mutant of Halobacterium halobium. A pigment absorbing approximately 590 nm halorhodopsin (HR) underwent a faster photocycle with a phototransient at approximately 490 nm (half-time of decay, tau 1/2 = 10 ms). Another third rhodopsinlike pigment (TR) absorbing approximately 580 nm underwent a slower photocycle accompanying a phototransient absorbing below 410 nm (tau 1/2 = 0.8s). The photocycles were measured under various conditions of temperature, NaCl concentration, pH, and in the presence of cholate. All results obtained support the notion that the two photocycles are independent of each other, and the fast or the slow cycle can be abolished after these treatments. At alkaline pH, the wavelength of maximum absorbance of both pigments shifted to blue, but the magnitude of the shift of the pigment undergoing the slow photocycle was much greater than the other. The ratio of the content of the two pigments varies among bacteriorhodopsin-free mutants.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(83)84277-5