Light-dependent trans to cis isomerization of the retinal in halorhodopsin.
Flash-induced absorption changes in the near UV were determined for bacteriorhodopsin and halorhodopsin on a millisecond time scale. The difference spectrum obtained for bacteriorhodopsin was comparable to model difference spectra of tyrosine (aromatic OH deprotonated vs protonated), as found by others. The flash-induced difference spectrum for halorhodopsin, in contrast, resembled a model spectrum obtained for trans to 13-cis isomerization of retinal in bacteriorhodopsin. A model for chloride translocation by halorhodopsin is presented, in which the retinal isomerization moves positive charges, which in turn modulate the affinity of a site to chloride.
D001436:Bacteriorhodopsins / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism*; D025602:Halorhodopsins; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D008954:Models, Biological; D012172:Retinaldehyde / Q000378:metabolism*; D012176:Retinoids / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
D025602:Halorhodopsins; D012176:Retinoids; D002338:Carotenoids; D001436:Bacteriorhodopsins; D012172:Retinaldehyde