tailieunhanh - Báo cáo khoa học: Purple membrane lipid control of bacteriorhodopsin conformational flexibility and photocycle activity An infrared spectroscopic study

Specific lipids of the purple membrane ofHalobacteriaare required for normal bacteriorhodopsin structure, function, and photocycle kinetics [Hendler, . & Dracheva, S. (2001) Biochemistry (Moscow)66, 1623–1627]. The decay of the M-fast intermediate through a path including the O intermediate requires the presence of a hydrophobic envi-ronment near four charged aspartic acid residues within the cytoplasmic loop region of the protein (R. W. Hendler & S. Bose, unpublished results). | Eur. J. Biochem. 270 1920-1925 2003 FEBS 2003 doi Purple membrane lipid control of bacteriorhodopsin conformational flexibility and photocycle activity An infrared spectroscopic study Richard W. Hendler1 Steven M. Barnett2 Swetlana Dracheva1 Salil Bose1 and Ira W. Levin2 1 Laboratory of Cell Biology National Heart Lung and Blood Institute and laboratory of Chemical Physics National Institute of Diabetes and Digestive and Kidney Diseases National Institutes of Health Bethesda MD 20892-0510 USA Specific lipids of the purple membrane of Halobacteria are required for normal bacteriorhodopsin structure function and photocycle kinetics Hendler . Dracheva S. 2001 Biochemistry Moscow 66 1623-1627 . The decay of the M-fast intermediate through a path including the O intermediate requires the presence of a hydrophobic environment near four charged aspartic acid residues within the cytoplasmic loop region of the protein R. W. Hendler S. Bose unpublished results . On the basis of the unique ability of squalene the most hydrophobic purple membrane lipid to induce recovery of M-fast activity in Triton-treated purple membrane we proposed that this uncharged lipid modulates an electrostatic repulsion between the membrane surface of the inner trimer space and the nearby charged aspartic acids of the cytoplasmic loop region to promote transmembrane a-helical mobility with a concomitant increase in the speed of the photocycle. We examined Triton-treated purple membranes in various stages of reconstitution with native lipid suspensions using infrared spectroscopic techniques. We demonstrate a correlation between the vibrational half-width parameter of the protein a-helical amide I mode at 1660 cm-1 reflecting the motional characteristics of the transmembrane helices and the lipid-induced recovery of native bacteriorhodopsin properties in terms of the visible absorbance maxima of ground state bacteriorhodopsin and the mean decay times of the .