title: Light-induced modulation of protein dynamics during the photocycle of bacteriorhodopsin.
abstract: Knowledge about the dynamical properties of a protein is of essential importance for understanding the structure-dynamics-function relationship at the atomic level. So far, however, the correlation between internal protein dynamics and functionality has only been studied indirectly in steady-state experiments by variation of external parameters like temperature and hydration. In the present study we describe a novel type of (laser-neutron) pump-probe experiment, which combines in situ optical activation of the biological function of a membrane protein with a time-dependent monitoring of the protein dynamics using quasielastic neutron scattering. As a first successful application we present data obtained selectively in the ground state and in the M-intermediate of bacteriorhodopsin (BR). Temporary alterations in both localized reorientational protein motions and harmonic vibrational dynamics have been observed during the photocycle of BR. This observation is a direct proof for the functional significance of protein structural flexibility, which is correlated with the large-scale structural changes in the protein structure occurring during the M-intermediate. We anticipate that functionally important modulations of protein dynamics as observed here are of relevance for most other proteins exhibiting conformational transitions in the time course of functional operation.
authors.affiliation: Max-Volmer-Laboratories for Biophysical Chemistry, Technische Universität Berlin, Berlin, Germany. joerg.pieper@tu-berlin.de
authors.forename: Jörg
authors.initials: J
authors.lastname: Pieper
authors.forename: Alexandra
authors.initials: A
authors.lastname: Buchsteiner
authors.forename: Norbert A
authors.initials: NA
authors.lastname: Dencher
authors.forename: Ruep E
authors.initials: RE
authors.lastname: Lechner
authors.forename: Thomas
authors.initials: T
authors.lastname: Hauss
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry*; D019605:Euryarchaeota / Q000737:chemistry / Q000528:radiation effects; D007834:Lasers; D008027:Light; D008958:Models, Molecular; D009502:Neutrons; D055668:Photochemical Processes; D017434:Protein Structure, Tertiary; D013057:Spectrum Analysis
chemical_list: D001436:Bacteriorhodopsins