The coupling ion in the methanoarchaeal ATP synthases: H⁺ vs. Na⁺ in the A₁Ao ATP synthase from the archaeon Methanosarcina mazei Gö1
2007
Pisa, Kim Y. | Weidner, Claudia | Maischak, Heiko | Kavermann, Holger | Müller, Volker
To establish a system to analyze ATP synthesis by the archaeal A₁Ao ATP synthase and to address the nature of the coupling ion, the operon encoding the A₁Ao ATP synthase from the mesophile Methanosarcina mazei Gö1 was cloned in an expression vector and it was expressed in the F₁Fo ATP synthase-negative mutant Escherichia coli DK8. Western blot analyses revealed that each of the subunits was produced, and the subunits assembled to a functional, membrane-embedded ATP synthase/ATPase. ATP hydrolysis was inhibited by dicyclohexylcarbodiimide but also by tributyltin, which turned out to be the most efficient inhibitor of the Ao domain of A₁Ao ATP synthase known to date. ATP hydrolysis was not dependent on the Na⁺ concentration of the medium, and inhibition of the enzyme by dicyclohexylcarbodiimide could not be relieved by Na⁺. The enzyme present in the cytoplasmic membrane of E. coli catalyzed ATP synthesis driven by an artificial ΔpH but not by ΔpNa or ΔμNa⁺.
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