Pathways of proton transfer in the light-driven pump bacteriorhodopsin.
The mechanism of proton transport in the light-driven pump bacteriorhodopsin is beginning to be understood.  Light causes the all-trans to 13-cis isomerization of the retinal chromophore.  This sets off a sequential and directed series of transient decreases in the pKa's of a) the retinal Schiff base, b) an extracellular proton release complex which includes asp-85, and c) a cytoplasmic proton uptake complex which includes asp-96.  The timing of these pKa changes during the photoreaction cycle causes sequential proton transfers which result in the net movement of a proton across the protein, from the cytoplasmic to the extracellular surface.
Lanyi
J K
JK
Department of Physiology and Biophysics, University of California, Irvine 92717.
D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology* / Q000528:radiation effects; D001436:Bacteriorhodopsins / Q000737:chemistry / Q000502:physiology* / Q000528:radiation effects; D002462:Cell Membrane / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology; D006217:Halobacterium / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D008027:Light; D008564:Membrane Potentials / Q000502:physiology; D017494:Proton Pumps / Q000502:physiology*; D012545:Schiff Bases
D001426:Bacterial Proteins; D017494:Proton Pumps; D012545:Schiff Bases; D001436:Bacteriorhodopsins