Related Experiment Video
Updated: Jul 14, 2026

Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells
Published on: October 1, 2010
Modes of operation of the BKCa channel beta2 subunit
Nicoletta Savalli1, Andrei Kondratiev, Sarah Buxton de Quintana
1Department of Anesthesiology-Division of Molecular Medicine, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, CA 90095, USA.
Abstract:
The beta(2) subunit of the large conductance Ca(2+)- and voltage-activated K(+) channel (BK(Ca)) modulates a number of channel functions, such as the apparent Ca(2+)/voltage sensitivity, pharmacological and kinetic properties of the channel. In addition, the N terminus of the beta(2) subunit acts as an inactivating particle that produces a relatively fast inactivation of the ionic conductance. Applying voltage clamp fluorometry to fluorescently labeled human BK(Ca) channels (hSlo), we have investigated the mechanisms of operation of the beta(2) subunit. We found that the leftward shift on the voltage axis of channel activation curves (G(V)) produced by coexpression with beta(2) subunits is associated with a shift in the same direction of the fluorescence vs. voltage curves (F(V)), which are reporting the voltage dependence of the main voltage-sensing region of hSlo (S4-transmembrane domain). In addition, we investigated the inactivating mechanism of the beta(2) subunits by comparing its properties with the ones of the typical N-type inactivation process of Shaker channel. While fluorescence recordings from the inactivated Shaker channels revealed the immobilization of the S4 segments in the active conformation, we did not observe a similar feature in BK(Ca) channels coexpressed with the beta(2) subunit. The experimental observations are consistent with the view that the beta(2) subunit of BK(Ca) channels facilitates channel activation by changing the voltage sensor equilibrium and that the beta(2)-induced inactivation process does not follow a typical N-type mechanism.
Related Concept Videos
Activation and Inactivation of G Proteins
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,...
ATP Synthase: Mechanism
Adrenergic Receptors: β Subtype
Isoprenaline > Adrenaline > Noradrenaline
Neurotransmitter binding to these receptors causes activation of adenylyl cyclase resulting in increased concentrations of cAMP and modulation of calcium ion channels within the cell. They are further classified into β1, β2, and β3 subtypes.
β1-adrenoceptors: β1-adrenoceptors have equal affinities for...
Cooperative Allosteric Transitions
cAMP-dependent Protein Kinase Pathways

