title: Chromophore distortions in the bacteriorhodopsin photocycle: evolution of the H-C14-C15-H dihedral angle measured by solid-state NMR.
abstract: In recent years, structural information about bacteriorhodopsin has grown substantially with the publication of several crystal structures. However, precise measurements of the chromophore conformation in the various photocycle states are still lacking. This information is critical because twists about the chromophore backbone chain can influence the Schiff base nitrogen position, orientation, and proton affinity. Here, we focus on the C14-C15 bond, using solid-state nuclear magnetic resonance spectroscopy to measure the H-C14-C15-H dihedral angle. In the resting state (bR(568)), we obtain an angle of 164 +/- 4 degrees, indicating a 16 degrees distortion from a planar all-trans chromophore. The dihedral angle is found to decrease to 147 +/- 10 degrees in the early M intermediate (M(o)) and to 150 +/- 4 degrees in the late M intermediate (M(n)). These results demonstrate changes in the chromophore conformation undetected by recent X-ray diffraction studies.
authors.affiliation: Department of Chemistry and Center for Magnetic Resonance, Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Lansing
authors.forename: Morten
authors.initials: M
authors.lastname: Hohwy
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Jaroniec
authors.forename: A F L
authors.initials: AF
authors.lastname: Creemers
authors.forename: Johan
authors.initials: J
authors.lastname: Lugtenburg
authors.forename: Judith
authors.initials: J
authors.lastname: Herzfeld
authors.forename: Robert G
authors.initials: RG
authors.lastname: Griffin
mesh_terms: D001436:Bacteriorhodopsins / Q000502:physiology*; D002244:Carbon / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D008027:Light; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D009584:Nitrogen / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D001436:Bacteriorhodopsins; D002244:Carbon; D006859:Hydrogen; D009584:Nitrogen