Studies of an acid-induced species of purple membrane from Halobacterium halobium.
A new spectral species of the purple membrane of Halobacterium halobium has been observed below pH 3.2. The formation of this new species is temperature-dependent and is favoured by increasing temperature up to the physiological range of the organism. The rate of formation at pH 3.0 and 22 degrees C is 7.9 x 10-3s-1. The spectral distribution and temperature-dependence of the new species suggest that it may be phototransiet O, stabilized by low pH. Flash-photolytic experiments in the pH range 7.2-2.7 show a pH-dependence corresponding to the static events and are consistent with a single protonation of bacteriorhodopsin below pH 3.22. These results can also be interpreted in terms of the stabilization of phototransient O at low pH. The temperature-dependence of the formation of the acid-induced species may reflect a relationship with the phase transition of the membrane.
D001436:Bacteriorhodopsins; D002338:Carotenoids; D055598:Chemical Phenomena; D002621:Chemistry; D006217:Halobacterium / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010782:Photolysis; D013053:Spectrophotometry; D013696:Temperature
D002338:Carotenoids; D001436:Bacteriorhodopsins