Light-induced modulation of protein dynamics during the photocycle of bacteriorhodopsin.
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.
Pieper
Jörg
J
Max-Volmer-Laboratories for Biophysical Chemistry, Technische Universität Berlin, Berlin, Germany. joerg.pieper@tu-berlin.de
Buchsteiner
Alexandra
A
Dencher
Norbert A
NA
Lechner
Ruep E
RE
Hauss
Thomas
T
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
D001436:Bacteriorhodopsins