This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.107.120386v1 95/1/194    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Wood, K. Articles by Oesterhelt, D. PubMed PubMed Citation Articles by Wood, K. Articles by Oesterhelt, D.

Hydration Dependence of Active Core Fluctuations in Bacteriorhodopsin

Kathleen Wood ^*  , Ursula Lehnert ^* , Brigitte Kessler , Giuseppe Zaccai ^*  and Dieter Oesterhelt 

^* Institut Laue-Langevin, BP 156, F-38042 Grenoble cedex 9, France; Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany; and Institut de Biologie Structurale Jean Pierre Ebel CEA-CNRS-UJF, F-38027 Grenoble cedex 1, France

Correspondence: Address reprint requests to G. Zaccai, ILL, BP 156, 6 rue Jules Horowitz, 38042 Grenoble cedex 9, France. Tel.: 33-4-76-20-7679; E-mail: zaccai{at}ill.fr.

We used neutron scattering and specific hydrogen-deuterium labeling to investigate the thermal dynamics of isotope-labeled amino acids and retinal, predominantly in the active core and extracellular moiety of bacteriorhodopsin (BR) in the purple membrane and the dynamical response to hydration. Measurements on two neutron spectrometers allowed two populations of motions to be characterized. The lower amplitude motions were found to be the same for both the labeled amino acids and retinal of BR and the global membrane. The larger amplitude dynamics of the labeled part, however, were found to be more resilient than the average membrane, suggesting their functional importance. The response to hydration was characterized, showing that the labeled part of BR is not shielded from hydration effects. The results suggest that the inhibition of high-amplitude motions by lowering hydration may play a key role in the slowing down of the photocycle and the proton pumping activity of BR.