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Charge displacements during ATP-hydrolysis and synthesis of the Na+-transporting FoF1-ATPase of Ilyobacter tartaricus |
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| Authors: | Burzik Christiane Kaim Georg Dimroth Peter Bamberg Ernst Fendler Klaus |
| Affiliation: | Max-Planck-Institut für Biophysik, D-60596 Frankfurt/Main, Germany. |
| Abstract: | Transient electrical currents generated by the Na(+)-transporting F(o)F(1)-ATPase of Ilyobacter tartaricus were observed in the hydrolytic and synthetic mode of the enzyme. Two techniques were applied: a photochemical ATP concentration jump on a planar lipid membrane and a rapid solution exchange on a solid supported membrane. We have identified an electrogenic reaction in the reaction cycle of the F(o)F(1)-ATPase that is related to the translocation of the cation through the membrane bound F(o) subcomplex of the ATPase. In addition, we have determined rate constants for the process: For ATP hydrolysis this reaction has a rate constant of 15-30 s(-1) if H(+) is transported and 30-60 s(-1) if Na(+) is transported. For ATP synthesis the rate constant is 50-70 s(-1). |
| Keywords: | BLM black lipid membrane SSM solid supported membrane NPE-caged ATP P3-1-(2-nitro)phenylethyladenosine-5′-triphosphate) background ATP ATP present in small amounts before and after activation of the ATPase λ rate constant of release of ATP from caged ATP η fraction of ATP released from caged ATP DCCD dicyclohexylcarbodiimide DTT dithiothreitole |
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