Calcium-activated potassium channel subunit beta-2 is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
that in humans is encoded by the ''KCNMB2''
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
.
are large conductance, voltage and calcium-sensitive
potassium channel
Potassium channels are the most widely distributed type of ion channel found in virtually all organisms. They form potassium-selective pores that span cell membranes. Potassium channels are found in most cell types and control a wide variety of cel ...
s which are fundamental to the control of smooth muscle tone and neuronal excitability. BK channels can contain two distinct subunits: a pore-forming alpha subunit and a modulatory beta subunit. Each complete BK channel contains four copies of the pore-forming alpha subunit and up to four beta subunits. The protein encoded by the KCNMB2 gene is an auxiliary beta subunit which influences the calcium sensitivity of BK currents and, following activation of BK current, causes persistent inactivation. The subunit encoded by the KCNMB2 gene is expressed in various endocrine cells, including pancreas and adrenal chromaffin cells. It is also found in the brain, including the hippocampus. The KCNMB2 gene is homologous to three other genes found in mammalian genomes:
KCNMB1
Calcium-activated potassium channel subunit beta-1 is a protein that in humans is encoded by the ''KCNMB1'' gene.
Function
MaxiK channels are large conductance, voltage and calcium-sensitive potassium channels which are fundamental to the cont ...
(found primarily in smooth muscle),
KCNMB3
Calcium-activated potassium channel subunit beta-3 is a protein that in humans is encoded by the ''KCNMB3'' gene.
MaxiK channels are large conductance, voltage and calcium-sensitive potassium channels which are fundamental to the control of smooth ...
, and
KCNMB4
Calcium-activated potassium channel subunit beta-4 is a protein that in humans is encoded by the ''KCNMB4'' gene.
MaxiK channels are large conductance, voltage and calcium-sensitive potassium channels which are fundamental to the control of smooth ...
(the primary brain BK auxiliary subunit).
Calcium-activated potassium channel subunit beta-2 comprises two
domains. An
N-terminal
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...
cytoplasmic
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. Th ...
domain, the
ball and chain domain, which is responsible for the fast inactivation of these channels,
and a C-terminal
calcium-activated potassium channel beta subunit domain. The N-terminal domain only occurs in calcium-activated potassium channel subunit beta-2, while the C-terminal domain is found in related proteins.
See also
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BK channel
BK channels (big potassium), are large conductance calcium-activated potassium channels, also known as Maxi-K, slo1, or Kca1.1. BK channels are voltage-gated potassium channels that conduct large amounts of potassium ions (K+) across the ce ...
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Voltage-gated potassium channel
Voltage-gated potassium channels (VGKCs) are transmembrane channels specific for potassium and sensitive to voltage changes in the cell's membrane potential. During action potentials, they play a crucial role in returning the depolarized ce ...
References
Further reading
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External links
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Protein domains
Ion channels
{{membrane-protein-stub