The proton-pumping and the ATP hydrolysis activities of the ATP synthase of Rhodobacter capsulatus have been compared as a function of the ADP and Pi concentrations. The proton pumping was measured either with the transmembrane pH difference probe, 9-amino-6-chloro-2-methoxyacridine, or with the transmembrane electric potential difference probe, bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol, obtaining consistent results. The comparison indicates that an intrinsic uncoupling of ATP synthase is induced when the concentration of either ligand is decreased. The half-maximal effect was found in the submicromolar range for ADP and at about 70 M for Pi. It is proposed that a switch from a partially uncoupled state of ATP synthase to the coupled state is induced by the simultaneous binding of ADP and Pi.

Physiological ligands ADP and Pi modulate the degree of intrinsic coupling in the ATP synthetase of the photosynthetic bacterium Rhodobacter capsulatus

TURINA, MARIA PAOLA;GIOVANNINI, DONATELLA;GUBELLINI, FRANCESCA;MELANDRI, BRUNO ANDREA
2004

Abstract

The proton-pumping and the ATP hydrolysis activities of the ATP synthase of Rhodobacter capsulatus have been compared as a function of the ADP and Pi concentrations. The proton pumping was measured either with the transmembrane pH difference probe, 9-amino-6-chloro-2-methoxyacridine, or with the transmembrane electric potential difference probe, bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol, obtaining consistent results. The comparison indicates that an intrinsic uncoupling of ATP synthase is induced when the concentration of either ligand is decreased. The half-maximal effect was found in the submicromolar range for ADP and at about 70 M for Pi. It is proposed that a switch from a partially uncoupled state of ATP synthase to the coupled state is induced by the simultaneous binding of ADP and Pi.
BIOCHEMISTRY
TURINA M.P.; GIOVANNINI D.; GUBELLINI F.; MELANDRI B.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/1834
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