A helical region in the C terminus of small-conductance Ca2+-activated K+ channels controls assembly with apo-calmodulin.Wissmann, R., Bildl, W., Neumann, H., Rivard, A.F., Klocker, N., Weitz, D., Schulte, U., Adelman, J.P., Bentrop, D., Fakler, B.
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- PubMed: 11723128
- DOI: 10.1074/jbc.M109240200
- PubMed Abstract:
- Mechanism of calcium gating in small-conductance calcium-activated potassium channels
Xia, X.-M.,Fakler, B.,Rivard, A.,Wayman, G.,Johnson-Pais, T.,Keen, J.E.,Ishii, T.,Hirschberg, B.,Bond, C.T.,Lutsenko, S.,Maylie, J.,Adelman, J.P.
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Keen, J.E.,Khawaled, R.,Farrens, D.L.,Neelands, T.,Rivard, A.,Bond, C.T.,Janowsky, A.,Fakler, B.,Adelman, J.P.,Maylie, J.
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- Structure of the gating domain of a Ca2+-activated K+ channel complexed with Ca2+/calmodulin
Schumacher, M.A.,Rivard, A.F.,Baechinger, H.P.,Adelman, J.P.
(2001) Nature 410: 1120
Small conductance Ca(2+)-activated potassium (SK) channels underlie the afterhyperpolarization that follows the action potential in many types of central neurons. SK channels are voltage-independent and gated solely by intracellular Ca(2+) in the sub ...
Small conductance Ca(2+)-activated potassium (SK) channels underlie the afterhyperpolarization that follows the action potential in many types of central neurons. SK channels are voltage-independent and gated solely by intracellular Ca(2+) in the submicromolar range. This high affinity for Ca(2+) results from Ca(2+)-independent association of the SK alpha-subunit with calmodulin (CaM), a property unique among the large family of potassium channels. Here we report the solution structure of the calmodulin binding domain (CaMBD, residues 396-487 in rat SK2) of SK channels using NMR spectroscopy. The CaMBD exhibits a helical region between residues 423-437, whereas the rest of the molecule lacks stable overall folding. Disruption of the helical domain abolishes constitutive association of CaMBD with Ca(2+)-free CaM, and results in SK channels that are no longer gated by Ca(2+). The results show that the Ca(2+)-independent CaM-CaMBD interaction, which is crucial for channel function, is at least in part determined by a region different in sequence and structure from other CaM-interacting proteins.
Department of Physiology II, University of Tübingen, Ob dem Himmelreich 7, 72074 Tübingen, Germany.