Structural dynamics of light-driven proton pumps.
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.
Andersson
Magnus
M
Department of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden.
Malmerberg
Erik
E
Westenhoff
Sebastian
S
Katona
Gergely
G
Cammarata
Marco
M
Wöhri
Annemarie B
AB
Johansson
Linda C
LC
Ewald
Friederike
F
Eklund
Mattias
M
Wulff
Michael
M
Davidsson
Jan
J
Neutze
Richard
R
D001436:Bacteriorhodopsins / Q000737:chemistry*; D008027:Light; D011487:Protein Conformation; D012243:Rhodopsin / Q000737:chemistry*; D025604:Rhodopsins, Microbial; D012542:Scattering, Radiation
D025604:Rhodopsins, Microbial; C413548:proteorhodopsin; D001436:Bacteriorhodopsins; D012243:Rhodopsin