title: Trans/13-cis isomerization is essential for both the photocycle and proton pumping of bacteriorhodopsin.
abstract: We studied an analogue of bacteriorhodopsin whose chromophore is based on all-trans retinal. A five-membered ring was built around the 13-14 double bond so as to prohibit trans to 13-cis isomerization. No light-induced photochemical changes were seen, other than those due to a small amount (approximately 5%) of unbleached bacteriorhodopsin remaining in the apomembrane used for regeneration. The techniques used included flash photolysis at room and liquid nitrogen temperatures and Fourier-transform infrared difference spectroscopy. When the trans-fixed pigment was incorporated into phospholipid vesicles, no evidence of light-initiated proton pumping could be found. The results indicate that trans to 13-cis isomerization is essential for the photochemical transformation and function of bacteriorhodopsin.
authors.forename: C H
authors.initials: CH
authors.lastname: Chang
authors.forename: R
authors.initials: R
authors.lastname: Govindjee
authors.forename: T
authors.initials: T
authors.lastname: Ebrey
authors.forename: K A
authors.initials: KA
authors.lastname: Bagley
authors.forename: G
authors.initials: G
authors.lastname: Dollinger
authors.forename: L
authors.initials: L
authors.lastname: Eisenstein
authors.forename: J
authors.initials: J
authors.lastname: Marque
authors.forename: H
authors.initials: H
authors.lastname: Roder
authors.forename: J
authors.initials: J
authors.lastname: Vittitow
authors.forename: J M
authors.initials: JM
authors.lastname: Fang
mesh_terms: D001436:Bacteriorhodopsins / Q000502:physiology* / Q000528:radiation effects; D002338:Carotenoids / Q000502:physiology*; D006217:Halobacterium; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D010777:Photochemistry; D010782:Photolysis; D011522:Protons; D013053:Spectrophotometry; D013055:Spectrophotometry, Infrared
chemical_list: D011522:Protons; D002338:Carotenoids; D001436:Bacteriorhodopsins