Related Experiment Video
Updated: May 10, 2026

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes
Published on: January 11, 2011
Structure of the gating domain of a Ca2+-activated K+ channel complexed with Ca2+/calmodulin
M A Schumacher1, A F Rivard, H P Bächinger
1Vollum Institute, Oregon Health Sciences University, Portland, Oregon 97201-3098, USA. schumacm@ohsu.edu
Abstract:
Small-conductance Ca2+-activated K+ channels (SK channels) are independent of voltage and gated solely by intracellular Ca2+. These membrane channels are heteromeric complexes that comprise pore-forming alpha-subunits and the Ca2+-binding protein calmodulin (CaM). CaM binds to the SK channel through the CaM-binding domain (CaMBD), which is located in an intracellular region of the alpha-subunit immediately carboxy-terminal to the pore. Channel opening is triggered when Ca2+ binds the EF hands in the N-lobe of CaM. Here we report the 1.60 A crystal structure of the SK channel CaMBD/Ca2+/CaM complex. The CaMBD forms an elongated dimer with a CaM molecule bound at each end; each CaM wraps around three alpha-helices, two from one CaMBD subunit and one from the other. As only the CaM N-lobe has bound Ca2+, the structure provides a view of both calcium-dependent and -independent CaM/protein interactions. Together with biochemical data, the structure suggests a possible gating mechanism for the SK channel.
Related Concept Videos
Assembly of Signaling Complexes
Interaction domains in cell signaling
Interaction domains recognize exposed features of their binding partners containing post-translationally modified sequences,...
Activation and Inactivation of G Proteins
G-Protein Gated Ion Channels
Sensory organs,...
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Structure of Cadherins
Ligand-Gated Ion Channel Receptor: Gating Mechanism

