Referenced in: none

Automatically associated channels: SK2

Title: A helical region in the C terminus of small-conductance Ca2+-activated K+ channels controls assembly with apo-calmodulin.

Authors: Ralph Wissmann, Wolfgang Bildl, Heinz Neumann, Andre F Rivard, Nikolaj Klöcker, Dietmar Weitz, Uwe Schulte, John P Adelman, Detlef Bentrop, Bernd Fakler

Journal, date & volume: J. Biol. Chem., 2002 Feb 8 , 277, 4558-64

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/11723128

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.