title: Structural dynamics of light-driven proton pumps.
abstract: Bacteriorhodopsin and proteorhodopsin are simple heptahelical proton pumps containing a retinal chromophore covalently bound to helix G via a protonated Schiff base. Following the absorption of a photon, all-trans retinal is isomerized to a 13-cis conformation, initiating a sequence of conformational changes driving vectorial proton transport. In this study we apply time-resolved wide-angle X-ray scattering to visualize in real time the helical motions associated with proton pumping by bacteriorhodopsin and proteorhodopsin. Our results establish that three conformational states are required to describe their photocycles. Significant motions of the cytoplasmic half of helix F and the extracellular half of helix C are observed prior to the primary proton transfer event, which increase in amplitude following proton transfer. These results both simplify the structural description to emerge from intermediate trapping studies of bacteriorhodopsin and reveal shared dynamical principles for proton pumping.
authors.affiliation: Department of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Andersson
authors.forename: Erik
authors.initials: E
authors.lastname: Malmerberg
authors.forename: Sebastian
authors.initials: S
authors.lastname: Westenhoff
authors.forename: Gergely
authors.initials: G
authors.lastname: Katona
authors.forename: Marco
authors.initials: M
authors.lastname: Cammarata
authors.forename: Annemarie B
authors.initials: AB
authors.lastname: Wöhri
authors.forename: Linda C
authors.initials: LC
authors.lastname: Johansson
authors.forename: Friederike
authors.initials: F
authors.lastname: Ewald
authors.forename: Mattias
authors.initials: M
authors.lastname: Eklund
authors.forename: Michael
authors.initials: M
authors.lastname: Wulff
authors.forename: Jan
authors.initials: J
authors.lastname: Davidsson
authors.forename: Richard
authors.initials: R
authors.lastname: Neutze
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry*; D008027:Light; D011487:Protein Conformation; D012243:Rhodopsin / Q000737:chemistry*; D025604:Rhodopsins, Microbial; D012542:Scattering, Radiation
chemical_list: D025604:Rhodopsins, Microbial; C413548:proteorhodopsin; D001436:Bacteriorhodopsins; D012243:Rhodopsin