Nonionic detergent effects on spectroscopic characteristics and the photocycle of bacteriorhodopsin in purple membranes.
Treatment of purple membranes isolated from Halobacterium halobium with nonionic detergents caused the following effects in addition to solubilizing bacteriorhodopsin: a blue shift of the absorption spectrum of bacteriorhodopsin; an increase in tryptophan fluorescence of about twofold; an enhanced rate of bleaching in the presence of hydroxylamine; and the disappearance of the negative exciton band in the CD spectrum at 600 nm. Crosslinking of purple membranes by glutaraldehyde can prevent solubilization of bacteriorhodopsin by detergents. However, only the effect on the CD spectrum by detergents can be inhibited by crosslinking of the purple membranes prior to detergent treatment. Photocycle kinetics studies revealed that the apparent pK of the slow component of the M412 decay was decreased by the detergent treatment while the rise time for M412 formation is accelerated two- to threefold. Crosslinking also did not prevent these effects. These results demonstrate that nonionic detergents, apart from their action to monomerize bacteriorhodopsin, also affect retinal-apoprotein interactions.
D001436:Bacteriorhodopsins / Q000302:isolation & purification*; D002338:Carotenoids / Q000302:isolation & purification*; D003902:Detergents / Q000494:pharmacology*; D006217:Halobacterium / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D010777:Photochemistry; D012995:Solubility; D013057:Spectrum Analysis; D013501:Surface-Active Agents / Q000494:pharmacology*
D003902:Detergents; D013501:Surface-Active Agents; D002338:Carotenoids; D001436:Bacteriorhodopsins