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1、CyclicSecondaryarticlePhotophosphorylationArticleContents.IntroductionHeinrichStrotmann,HeinrichHeineUniversity,Du¨sseldorf,Germany.EvidencefortheOccurrenceofFerredoxin-mediatedCyclicPhosphorylationinPlantPhotosynthesisJu¨rgenSchumann,HeinrichHeineUniversity,Du¨sseldorf,Germany
2、.PathwayofCyclicElectronTransport121.H/eandH/ATPStoichiometriesCyclicphotophosphorylationistheformationofATPcoupledtolight-dependentcyclic.Summary1electrontransportinchloroplastswithoutnetreductionofNADP.Introductionandcyclicelectrontransportinvolvesquinones,theCyclicphotophosp
3、horylationreferstotheformationofcytochromeb/c1complex,andasolublecytochromec2.1PartoftheconservedenergyisneededtofacilitateNADATPfromADPandphosphateinchloroplastscoupledtoreductionbyanexternalelectrondonorsuchassuccinatelight-drivencyclicelectrontransport,thatiselectroninalight
4、-independentuphillelectrontransport.Asecondtransportwithoutnetoxidationandreductionofaterminaldonorandacceptor,respectively.Itdiffersfromcytochrome(cy)foundinRhodospirillumcapsulatummaysupportphotosyntheticelectrontransportbutfunctionsnoncyclicphotophosphorylationcoupledtothelin
5、ear1mainlyintherespiratoryelectronflow(Myllykallioetal.,electrontransportfromwatertoNADP.Thelatter1999).ThephotosystemofChlorobiumresemblesPSI;itincludesphotosystemII(PSII)andphotosystemI(PSI),driveseithercyclicelectrontransportcoupledtoATPwhereastheformercomprisesonlyPSI.Bothel
6、ectronformationorlinearelectrontransportleadingtothepathwayspumpprotonsacrossthethylakoidmembrane,122reductionofNADbyanexternalelectrondonor(S,thusforminganelectrochemicalprotonpotentialdiffer-22ence,whichistheactualenergysourcefortheendergonicS2O3).phosphorylationofADP.Hence‘cy
7、clic’or‘noncyclic’referstotheelectrontransportpathwaythatgeneratesthedrivingforce,nottothemechanismofATPformation.ATPformationcoupledtoelectrontransportfromwaterEvidencefortheOccurrenceoftooxygenhasbeendesignated‘pseudocyclicphosphoryla-Ferredoxin-mediatedCycliction’asoxygenevo
8、lutionbywatercleavageisbalancedbyoxygenconsumptionatth
