Light-induced denaturation of bacteriorhodopsin solubilized by octyl-beta-glucoside.
The structural stability of bacteriorhodopsin (bR) solubilized by octyl-beta-glucoside was studied by measuring the denaturation kinetics under visible light irradiation and in the dark. The denaturation of bR solubilized by 50 mM octyl-beta-glucoside was very slow at room temperature when it was left in the dark. However, its spontaneous denaturation was accelerated when the solubilized bR was irradiated by visible light. The denaturation kinetics under visible light irradiation and in the dark could be well described by a single decay constant. The activation energy for the denaturation of bR was estimated from the temperature dependence of decay time constants. The activation energy under visible light irradiation was 12.5 kcal/mol, which was much smaller than the corresponding value in the dark, 26.2 kcal/mol. These results strongly suggest that some of the photointermediate states are less stable than the ground state of bR. The critical temperature and the activation energy for denaturation of bR in the solubilized state were much lower than those in the 2D crystalline state. Comparing the denaturation behavior in the 2D crystalline state and that in the octyl-beta-glucoside-solubilized state, our findings suggest that protein-protein interaction contributes to the stability of this protein.
Mukai
Y
Y
Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo, Hokkaido 060-0812, Japan.
Kamo
N
N
Mitaku
S
S
D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000528:radiation effects; D005960:Glucosides / Q000737:chemistry*; D019617:Halobacterium salinarum / Q000737:chemistry; D007700:Kinetics; D008027:Light; D011489:Protein Denaturation; D012995:Solubility; D013057:Spectrum Analysis; D013816:Thermodynamics
D005960:Glucosides; C018619:octyl-beta-D-glucoside; D001436:Bacteriorhodopsins