Download MendeleyA 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.(2002) J Biol Chem 277: 4558-4564
- PubMed: 11723128
- DOI: https://doi.org/10.1074/jbc.M109240200
- Primary Citation of Related Structures:
1KKD - PubMed Abstract:
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.
Organizational Affiliation:
Department of Physiology II, University of Tübingen, Ob dem Himmelreich 7, 72074 Tübingen, Germany.
