Mechanism of Conversion of Light into Chemical Energy in Bacteriorhodopsin: Identification of Charge Movements and Coupling to Active Site Conformational Changes
Annual rept. Apr 1987-Jun 1988
MONTANA STATE UNIV BOZEMAN DEPT OF CHEMISTRY
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Bacteriorhodopsin is the best understood transmembrane ion pump. Bacteriorhodopsin creates ca. 100 mV transmembrane potential by pumping protons across its membrane when illuminated by visible light. Visible light isomerizes a small ca. 300 Dalton chromophore called retinal which drives protein conformational changes that accomplish the pumping. Pumping occurs in a series of steps, and the intermediate forms can be trapped for study at sufficiently low temperatures. New methods of solid state NMR have recently provided striking new information on the detailed structure of the retinal active site in bacteriorhodopsin. However, the light induced changes that produce transmembrane proton pumping have not been studied. Experiments underway are designed to reveal the light induced conformational changes at the active site, the light induced charge movements, and the coupling of the charge motion to the active site conformational changes in bacteriorhodopsin using new solid state NMR methods.