potassium large conductance calcium-activated channel, subfamily M, alpha member 1 Synonyms: Slo1 Slo BKCa mSlo MaxiK mSlo1 kcnma1. Symbol: Kcnma1
KCNMA1 (also known as SLO; BKTM; SLO1; MaxiK; SAKCA; mSLO1; KCa1.1; MGC71881; SLO-ALPHA; bA205K10.1; DKFZp686K1437) encodes Slo1, a potassium large conductance calcium-activated channel, subfamily M, alpha member 1. MaxiK channels are fundamental to the control of smooth muscle tone and neuronal excitability. MaxiK channels can be formed by 2 subunits: the pore-forming alpha subunit, which is the product of this gene, and the modulatory beta subunit. Intracellular calcium regulates the physical association between the alpha and beta subunits. Alternatively spliced transcript variants encoding different isoforms have been identified.
Kcnma1 : potassium large conductance calcium-activated channel, subfamily M, alpha member 1
Double layer of lipid molecules that encloses all cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins.
apical plasma membrane
The region of the plasma membrane located at the apical end of the cell.
integral to membrane
Penetrating at least one phospholipid bilayer of a membrane. May also refer to the state of being buried in the bilayer with no exposure outside the bilayer. When used to describe a protein, indicates that all or part of the peptide sequence is embedded in the membrane.
A membrane raft that forms small pit, depression, or invagination that communicates with the outside of a cell and extends inward, indenting the cytoplasm and the cell membrane. Examples include any of the minute pits or incuppings of the cell membrane formed during pinocytosis. Such caveolae may be pinched off to form free vesicles within the cytoplasm.
voltage-gated potassium channel complex
A protein complex that forms a transmembrane channel through which potassium ions may cross a cell membrane in response to changes in membrane potential.
The membrane surrounding a cell that separates the cell from its external environment. It consists of a phospholipid bilayer and associated proteins.
The irregular network of unit membranes, visible only by electron microscopy, that occurs in the cytoplasm of many eukaryotic cells. The membranes form a complex meshwork of tubular channels, which are often expanded into slitlike cavities called cisternae. The ER takes two forms, rough (or granular), with ribosomes adhering to the outer surface, and smooth (with no ribosomes attached).
A specialized area of membrane facing the presynaptic membrane on the tip of the nerve ending and separated from it by a minute cleft (the synaptic cleft). Neurotransmitters across the synaptic cleft and transmit the signal to the postsynaptic membrane.
external side of plasma membrane
The side of the plasma membrane that is opposite to the side that faces the cytoplasm.
Any constituent part of the cytoplasm, all of the contents of a cell excluding the plasma membrane and nucleus, but including other subcellular structures.
Terminal inflated portion of the axon, containing the specialized apparatus necessary to release neurotransmitters. The axon terminus is considered to be the whole region of thickening and the terminal button is a specialized region of it.
Carbon monoxide (CO) is a potent activator of slo1 when heterologously expressed in human embryonic kidney 293 (HEK
293) cells (Jaggar , Williams ) or when natively expressed in vascular
myocytes (Jaggar , Wang , Wang ) and carotid body glomus cells (Riesco-Fagundo ).
BK channels are activated by voltage, intracellular Ca2+ and Mg2+ (Fig. 1 a, b in Yang , Larorre , Magleby , Hou ).
Hemoxygenase (hemeoxygenase-2; HO-2) is a
protein partner closely associated with the BKCa channel
complex (Williams ).
A motif in the S9–S10 part of the C-terminal of Slo1 is essential for CO activation. (Williams )
Sequence homology and experimental evidence suggest that the
structure of the voltage sensor domain (VSD) in BK channels may resemble that of other Kv channels19, while the
cytoplasmic domain of BK channels may adopt a similar structure as that of the MthK channel (Jiang , Hou , Shi , Yang , Jiang , Fodor ). Previous studies on Mg2+-dependent activation of BK channels have
revealed structural details that are important for BK channel function. Particularly, two acidic
amino acids (Glu374 and Glu399) in the cytoplasmic RCK1 domain of BK channel may
contribute to Mg2+ coordination (Yang , Xiao ). Removal of the side chain carboxylate groups from
these two residues completely abolishes Mg2+ sensing. These residues in the cytoplasmic
domain are located close to the C-terminus of the transmembrane segment S4, enabling the
bound Mg2+ to engage in an electrostatic interaction with the voltage-sensing residue Arg213
at the C-terminus of S414 (Fig. 1c in Yang ).
Slo1 is natively expressed in vascular
myocytes ( Jaggar , Wang , Wang ) and carotid body glomus cells (Riesco-Fagundo ).
Regulation by CO of BKCa channels is emerging as a
widespread and physiologically important phenomenon that
is intimately involved in the control of smooth muscle
contractility (both systemic and pulmonary) and excitability
of neurosecretory and neuronal cell populations. (Williams )