Effect of salt on photo cycle and ion pumping of halo rhod opsin and 3rd rhod opsin like pigment of halobacterium halobium
Hazemoto, N.; Kamo, N.; Kobatake, Y.; Tsuda, M.; Terayama, Y.
Biophysical Journal 45(6): 1073-1078
ISSN/ISBN: 0006-3495 Accession: 005267824
The cytoplasmic membranes of H. halobium contain at least 3 retinal pigments: bacteriorhodopsin (bR), halorhodopsin (hR) and a third rhodopsin-like pigment (tR). The amplitudes of the phototransient in the photolysis of hR and tR were measured in various salt solutions. Halogen ion (except fluoride) was required to retain the photocycle of hR. Parallels between the amplitude of the phototransient of hR and the magnitude of the photo-induced tetraphenylphosphonium uptake suggests that hR is a light-driven halogen pump, which supports the hypothesis by Schobert and Lanyi. The order of effectiveness of halogen was Br- > Cl- > I-. No specific ion was required to retain the photocycle of tR, and tR was concluded to be nonelectrogenic.