Butyl conformational reorganization as a possible explanation for the longitudinal flexibility of the binding site of bacteriorhodopsin. The azulene and C-22 retinoid analogs.
The UV-VIS absorption data of four bacteriorhodopsin (BR) analogs formed from azulene-retinals of varying polyene chain length show that the one-bond-shortened to one-bond-lengthened analogs possess comparable opsin shift values to that of BR. A two-bond-shortened analog exhibited a much smaller opsin shift. These data, combined with those reported for the C-22 retinal analog (Tokunaga et al., 1977, Biophys. J. 19, 191-198) were analyzed by molecular modelling and computer graphics in terms of a model where conformational flexibility of the appended butyl is the controlling factor in determining ease of pigment formation and protein/substrate interaction.
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Department of Chemistry, University of Hawaii, Honolulu 96822.
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D052176:Azulenes; D001436:Bacteriorhodopsins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D003196:Computer Graphics; D003508:Cycloheptanes / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D012176:Retinoids / Q000378:metabolism*; D013329:Structure-Activity Relationship
D052176:Azulenes; D003508:Cycloheptanes; D012176:Retinoids; D001436:Bacteriorhodopsins; C005525:azulene