Altered activity of bacteriorhodopsin in high concentrations of guanidine hydrochloride.

Bacteriorhodopsin from Halobacterium halobium was stable and active in high concentrations of guanidine hydrochloride. However the decay of the intermediate with absorption maximum at 407 nm and the uptake of protons from the medium were remarkably delayed. At alkaline pH values, all the molecules of bacteriohodopsin existed as the 407 nm intermediate in the light, and one proton per bacteriorhodopsin molecule was released.