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Bacteriorhodopsin
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  • Bacteriorhodopsin

  • Halobacterium halobiumResides in hypertonic environments (shallow waters of San Francisco bay)Diatomic oxygen is plentiful = OXPHOSDiatomic oxygen unavailable = LIGHT HARVESTINGAchieved by Bacteriorhodopsin, a 26 KD protein with all-trans-retinal attachedLIGHT IS CONVERTED DIRECTLY INTO A H+ MOTIVE FORCEF0F1 ATPaseH++ + + + + + + - - - - - - - - - H+ATPhv

  • Retinal is bound to LysineH+ pumping

  • PhotocycleThe energy trapping conformational transition occurs within one psDeprotonation and reprotonation steps are characterized by intermediates which contain distinct absorption spectraOne full turn of the cycle occurs within a msHence each step has a characteristic colourEvery sec, 50 protons are exportedOne question remainshow does the light induced isomerization of this protein drive H+ translocation

  • Bacteriorhodopsin is a Dynamic, Transmembrane ProteinSeveral transmem spanning helices3 Tyr hold the BR in placeRetinal sits at the junction separating the twohalf channels Notice the Bacteriorhodopsin is surrondedby Asp and Arg

  • Aspartate and Arginine are involved in the translocation process