Sodium ion cycling mediates energy coupling between complex I and ATP synthase

AUTOR(ES)

Gemperli, Anja C.

FONTE

The National Academy of Sciences

RESUMO

We show here sodium ion cycling between complex I from Klebsiella pneumoniae and the F1F0 ATP synthase from Ilyobacter tartaricus in a reconstituted proteoliposome system. In the course of NADH oxidation by complex I, an electrochemical sodium ion gradient was established and served as a driving force for the synthesis of ATP from ADP and phosphate. In the opposite direction, the Δμ̃Na+ generated by ATP hydrolysis could be coupled to NADH formation by reversed electron transfer from ubiquinol to NAD. For reverse electron transfer, a transmembrane voltage larger than 30 mV was obligatory. No NADH-driven proton transport into the lumen of proteoliposomes was detected. We conclude that Na+ is used as the exclusive coupling ion by the enterobacterial complex I.

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