examcoo §9 Transport across biomembrane

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1、§9Transportacrossbiomembrane缬氨霉素(valinomycin)的抗菌机理环形肽Transporters(permeases)Carriers(enzyme-like)Channels(gate-like)PassivetransportersActivetransportersPrimaryactivetransportersSecondaractivetransporters(needATPorlight)(needelectrochemicalgradientdirectly,ATPindirectl

2、y)Channels(1)HOchannels2(2)IonchannelsLigand-gatedionchannels:2,3,4Voltage-gatedionchannels:1(3)Ionselectivityinchannelsligand-gatedionchannelsPlaceLigandsChannelforAcetylcholineNa+，K+，Ca2+Serotonin血清素Na+，K+，Ca2+(5-hydroxytryptamine)extracellularglutamateNa+，K+，Ca2+gl

3、ycineCl－γ-aminobutyricacid(GABA)Cl－，K+cAMPK+，Ca2+IntracellularcGMPNa+，Ca2+（secondIPCa2+messengers）3Ca2+Cl－Waterchannels80年代中期,JohnHopkins大学的PeterAgre等从血细胞膜纯化Rh抗原的32kDa单元时发现一个28kDa的蛋白总会被一同提纯出来，以为这是Rh蛋白的降解产物。后来意识到这是一种以前没有被发现的蛋白，命名为CHIP28。PeterAgre等将CHIP28mRNA注入蛙卵细胞，发现表达了

4、CHIP28的蛙卵细胞迅速膨胀直至破裂,而没有CHIP28mRNA的细胞则几乎没有变化。CHIP28renamedasaquaporin1(AQP1)TopologyofasubunitWaterchannelformedbyasubunittetramersHOselectivityofAQP2Acetylcholine-gatedionchannelsThischannelallowsreadypassagetoNa+,Ca2+andK+,butothercationsandallanionsareunabletopassStr

5、uctureofAch-gatedChannelα,β,γ,δsubunitsarehomologousCationselectivityofAch-gatedchannelOpen-closemechanismofAch-gatedchannelVoltage-gatedNa+ionchannelsNa+channel:anlargeαandasmallβsubunitAllvoltage-gatedionchannelshaveasimilarαarchitectureS4–relatedtovoltagesensing,isf

6、oundinallvoltagegatedionchannelsandisabsentinligandgatedchannelsArchitectureofαsubunitinmembraneFunctionsofSandS46FourαsubunitscomplexoftheK+channelinratbraincells(fourβsubunitsnotshow)outsideinsideIonselectivityinchannels认识有限，目前了解较多的是一种细菌中的钾离子通道FouridenticalsubunitsM

7、odeloftheK+channelofbacteriaSelectivityfilterofbacterialK+channelSelectivityfilterofbacterialK+channelRestingMembranePotentialActionPotential29PropagationofActionPotentialsinNerveFiberSynaptictransmissionSomeinhibitorsofionchannelsVoltage-gatedNa+channelsTetrodot

8、oxin(河豚毒素←河豚)Saxitoxin(蛤蚌毒素←腰鞭毛虫)Voltage-gatedK+channelsDendrotoxin(树木毒素←树眼睛蛇)Ach-gatedionchannelsTubocur