Doctor Richard Neutze
Institute for Molecular Biotechnology
Chalmers University of Technology
Gothenburg, Sweden

Thursday, March 15, 2001
2:00 pm (CT)
3269 Beckman Institute

Abstract

The X-ray structure of the K-intermediate of bacteriorhodopsin's photocycle, trapped at low temperature, shows that the initial structural response of the simplest known light-driven proton pump is localized near the active site. Specifically, a key water molecule, located in the ground state between the Schiff base (the primary proton donor) and Asp85 (the primary proton acceptor) is dislocated, allowing Asp85 to approach the position originally occupied by the Schiff base and paving the way for further movement downstream in the photocycle. The structural rearrangements of later intermediate states progressing through the photocycle illustrates how the early structural rearrangements observed in K evolve first towards the extracellular side, and then the cytoplasmic side, of the protein. Furthermore, this molecular movie provides key insights into the role of active site water molecules and charged groups in dictating the overall vectorial nature of proton pumping by bacteriorhodopsin. Methodology and spectral aspects of the work are emphasized.