1KKD: Solution structure of the calmodulin binding domain (CaMBD) of small conductance Ca2+-activated potassium channels (SK2)

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.
PDB ID: 1KKDDownload
MMDB ID: 71125
PDB Deposition Date: 2001/12/7
Updated in MMDB: 2009/07
Experimental Method:
solution nmr
Source Organism:
Similar Structures:
Molecular Components in 1KKD
Label Count Molecule
Protein (1 molecule)
Small Conductance Calcium-activated Potassium Channel Protein 2(Gene symbol: Kcnn2)
Molecule annotation
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