膜蛋白的结构与功能三BacteriorhodopsinIntroductiontobacteriorhodopsinArchaebacteriaHalobacteriaSalinariumarethesourceofbacteriorhodopsinTheyarehalophilicbacteria()BacteriorhodopsinThepurplemembranepatchesareareasonthemembranewhereBRisconcentratedBRabsorbslightat570nm(visiblegreenlight)RedandBluelightisreflected,,28lipidmolecules,and8410watermolecules,,followingahexagonalsymmetry,—bacteriorhodopsinfunctionsasaprotonpump—BacteriorhodopsinuseslightenergytopumpH+totheexteriorofthecell,thusgeneratingaH+electrochemicalgradient,orproton-motiveforce—Photonsreactwithaboundretinalgroupcausingconformationalchangeinbacteriorhodopsin—Thecellsusethisproton-motiveforcetosynthesiseATPandtoperformothervitalfunctionsrequiringenergyexpenditureBacteriorhodopsinBacteriorhodopsintakesenergyfromphotonsThisenergyisconvertedandcreatesaprotongradientbypumpingprotonsoutsidethecellProtonsareallowedbackintothecellbyanATPsynthaseInanutshell:PhotonsareusedtopowerthecellBacteriorhodopsinExtracellularmatrixCytosolOKHH-D85deprotonated-PRSreprotonated-backtosquare1untilanotherprotonisomerizestheAll-transretinalPRSHH+EarlyElectronMicroscopyStudiesofBacteriorhodopsinBacteriorhodopsinnaturallyforms2-%ofpurplemembrane&bRistheother75%.Firstmembraneproteinstructure:Henderson&Unwin,Nature257,28-32(1975).Electronmicrographsfrom1mm2×45Åsamples(120,000proteinmolecules).Diffractionpatternisnotathreedimensionallatticeofpoints,,
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