KCNN2
KCNN2 (potassium calcium-activated channel subfamily N member 2, also known as KCa2.2 or hSK2) is a small conductance calcium-activated potassium channel. It opens in response to intracellular calcium through a constitutive association with calmodulin, and it contributes to neuronal excitability and cardiac repolarisation. Browse Assay Genie's current range of KCNN2 research reagents below, or read on for the biology behind the target.
KCNN2 is a small conductance calcium-activated potassium channel that mediates the voltage-independent transfer of potassium across the cell membrane. It is bound constitutively to calmodulin, in a calcium-independent manner. Channel opening is triggered when calcium binds calmodulin, producing a rotary movement that leads to formation of a dimeric complex and opens the gate. The resulting current is activated by rising intracellular calcium, not by voltage, and has a single-channel conductance of about 3 picosiemens.
The channel also shows inward rectification, which reduces its already small outward potassium conductance, particularly at membrane potentials above +20 mV. This may reflect blockade of the outward current by intracellular divalent cations such as calcium and magnesium, or an intrinsic property of the channel pore. Three positively charged amino acids in the S6 transmembrane domain, close to the pore, collectively control conductance and rectification through an electrostatic mechanism. The same residues influence the intrinsic open probability in the absence of calcium and the apparent calcium affinity for activation. The KCNN2 protein is an integral membrane protein that assembles with three other calmodulin-binding subunits to form the channel. UniProt also records it at the sarcomere Z line, and it plays a role in the repolarisation phase of the cardiac action potential.
In vertebrate neurons, action potentials are followed by an afterhyperpolarisation (AHP), whose components are carried by different calcium-activated potassium channels. The KCNN2 gene product is activated before membrane hyperpolarisation and is thought to regulate neuronal excitability by contributing to the slow component of the synaptic AHP. The gene belongs to the KCNN family and sits in the HGNC group of potassium calcium-activated channels. Alternative splicing produces multiple transcript variants. Mouse and rat both carry a Kcnn2 ortholog.
KCNN2 is thought to regulate neuronal excitability by contributing to the slow component of the synaptic afterhyperpolarisation that follows action potentials.
The channel plays a role in the repolarisation phase of the cardiac action potential, making it relevant to studies of cardiac excitability.
Constitutive calmodulin binding couples intracellular calcium to channel opening, providing a model for calcium-dependent gating of potassium channels.
Charged S6 residues near the pore control conductance, rectification and intrinsic open probability, supporting structure–function work on pore electrostatics.
KCNN2 forms a small conductance potassium channel that opens when calcium binds its associated calmodulin. Its activation is voltage-independent. It is thought to shape neuronal afterhyperpolarisation and excitability, and it contributes to repolarisation of the cardiac action potential.
KCNN2 is also called KCa2.2 and hSK2, and its protein name is small conductance calcium-activated potassium channel protein 2. Earlier HGNC names described it as a potassium intermediate/small conductance calcium-activated channel, subfamily N, member 2. Alternative splicing gives multiple transcript variants.
Mouse and rat each have a Kcnn2 ortholog. In humans, KCNN2 belongs to the KCNN potassium channel family, within the KCa2.2 subfamily, alongside related members such as KCNN3. Check the datasheet of any product for its validated reactivity.
Other members of the KCNN potassium channel family with products at Assay Genie.
Gene and protein annotations from HGNC, NCBI Gene and UniProt Q9H2S1; product specifications from Assay Genie datasheets.