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RESEARCH PRODUCT
Kinetics of proton release and uptake by channelrhodopsin-2
Tom ReslerCristiano ViappianiChristian BamannErnst BambergStefania AbbruzzettiBernd-joachim SchultzRamona SchlesingerAna-nicoleta BondarCoral Del ValMelanie NackIonela RaduJoachim Heberlesubject
Models MolecularRhodopsinProtonKineticsBiophysicsAnalytical chemistryChannelrhodopsinBacteriorhodopsinBiochemistry530Protein Structure SecondaryProton transferStructural BiologyGeneticsMolecular BiologyIon channelMembrane potentialbiologyChemistryfungiBacteriorhodopsinBiological TransportCell BiologyHydrogen-Ion ConcentrationProton PumpsOptogeneticsKineticsRhodopsinBiophysicsbiology.proteinProtonsIon channelStoichiometrydescription
Electrophysiological experiments showed that the light-activated cation channel channelrhodopsin-2 (ChR2) pumps protons in the absence of a membrane potential. We determined here the kinetics of transient pH change using a water-soluble pH-indicator. It is shown that ChR2 released protons prior to uptake with a stoichiometry of 0.3 protons per ChR2. Comparison to the photocycle kinetics revealed that proton release and uptake match rise and decay of the View the MathML sourceP3520 intermediate. As the View the MathML sourceP3520 state also represents the conductive state of cation channeling, the concurrence of proton pumping and channel gating implies an intimate mechanistic link of the two functional modes. Studies on the E123T and S245E mutants show that these residues are not critically involved in proton translocation.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2012-03-15 |