Lipid-protein interactions in the purple membrane: structural specificity within the hydrophobic domain.
In the absence of native-like interactions between bacteriorhodopsin and its neighbouring lipids, the pigment chromophore is reversibly titrated from its purple 570 nm form to a blue-shifted 480 nm form in the moderately alkaline pH range. Quantitation of this acid-base chromophore equilibrium in vesicles prepared from modified lipid mixtures shows that it is absent under conditions where bacteriorhodopsin is allowed to interact with methyl-substituted alkyl chains. The peculiar homogeneous structure of purple membrane alkyl chain lipids is thus likely to be an essential requirement for maintenance of the native bacteriorhodopsin structure over a wide pH range.
Pomerleau
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V
Centre de Recherche en Photobiophysique, Université du Québec à Trois-Rivières, Canada.
Harvey-Girard
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E
Boucher
F
F
D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000302:isolation & purification; D019617:Halobacterium salinarum / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010743:Phospholipids / Q000737:chemistry*; D018717:Purple Membrane / Q000737:chemistry*; D013053:Spectrophotometry; D013329:Structure-Activity Relationship
D010743:Phospholipids; D001436:Bacteriorhodopsins