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Cation binding in Na,K-ATPase, investigated by 205Tl solid-state NMR spectroscopy.

Jakobsen LO, Malmendal A, Nielsen NC, Esmann M

Department of Biophysics, Institute of Physiology and Biophysics, University of Aarhus, DK-8000 Aarhus, Denmark.

Cation binding to Na,K-ATPase is characterized in native membranes at room temperature by solid-state NMR spectroscopy using the K(+) congener (205)Tl. It has been demonstrated that the signals from occluded Tl(+) and nonspecifically bound Tl(+) can be detected and distinguished by NMR. Effects of dipole-dipole coupling between (1)H and (205)Tl in the occlusion sites show that the ions are rigidly bound, rather than just occluded. Furthermore, a low chemical shift suggests occlusion site geometries with a relatively small contribution from carboxylate and hydroxyl groups. Nonspecific binding of Tl(+) is characterized by rapid chemical exchange, in agreement with the observed low binding affinity.

Published 30 August 2006 in Biochemistry, 45(35): 10768-76.
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