| Literature References | 1. MINOR, D.L., JR., MASSELLING, S.J., JAN, Y.N. AND JAN, L.Y.
Transmembrane structure of an inwardly rectifying potassium channel.
CELL 96 879-891 (1999).
2. DOUPNIK, C.A., DAVIDSON, N. AND LESTER, H.A.
The inward rectifier potassium channel family.
CURR.OPIN.NEUROBIOL. 5 268-277 (1995).
3. REIMANN, F. AND ASHCROFT, F.M.
Inwardly rectifying potassium channels.
CURR.OPIN.CELL BIOL. 11 503-508 (1999).
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| Documentation | Potassium channels are found in virtually all cell types. Their pore-
forming subunits fall into three structural families, i.e. those possessing
six, four and two transmembrane (TM) domains. The six-TM domain K+ channels
can be further subdivided into six families: the voltage-gated K+ channels
(Kv), the KCNQ channels, the eag-like K+ channels, and three Ca2+-activated
K+ channels. Inwardly-rectifying K+ channels (Kir) are the principal class
of two-TM domain K+ channels, and the recently-discovered two-pore domain
K+ channels, make up a family of four-TM domain K+ channels.
Inwardly rectifying potassium channels (Kir) are responsible for regulating
diverse processes including: cellular excitability, vascular tone, heart
rate, renal salt flow, and insulin release [1]. To date, around twenty
members of this superfamily have been cloned, which can be grouped into six
families by sequence similarity, and these are designated Kir1.x-7.x [2,3].
Cloned Kir channel cDNAs encode proteins of between ~370-500 residues,
containing two predicted TM domains, with the characteristic K+ channel
pore-forming domain located between them. Both N- and C-termini are thought
to be cytoplasmic, and the N-terminus lacks a signal sequence. It is thought
that four Kir subunits assemble to form a tetrameric channel complex, which
may be hetero- or homomeric [1].
The Kir3.x channel family are gated by G proteins following G-protein
coupled receptor (GPCR) activation. They are widely distributed in
neuronal, atrial, and endocrine tissues and play key roles in generating
late inhibitory postsynaptic potentials, slowing the heart rate and
modulating hormone release. They are directly activated by G protein beta-
gamma subunits released from G protein heterotrimers of the G(i/o) family
upon appropriate receptor stimulation.
Kir3.1 channels are thought to form heteromers in vivo: in heart,
consisting of Kir3.1 and Kir3.2, and in brain, Kir3.1 with Kir 3.4.
KIR31CHANNEL is a 12-element fingerprint that provides a signature for the
Kir3.1 inward rectifier K+ channel. The fingerprint was derived from an
an initial alignment of 3 sequences: the motifs were drawn from conserved
regions spanning virtually the full alignment length, focusing on those
sections that characterise Kir3.1 but distinguish it from other subtypes -
motif 1 encodes the first 24 residues of the putative cytoplasmic
N-terminus; motif 2 lies between the first TM domain and the following pore
-forming (H1) domain; and motifs 3-12 encode portions of the cytoplasmic
C-terminus. A single iteration on SPTR37_10f was required to reach
convergence, no further sequences beiing identified beyond the starting
set.
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| Sequence Titles | IRK3_CHICK G PROTEIN-ACTIVATED INWARD RECTIFIER POTASSIUM CHANNEL 1 (GIRK1) (POTASSIUM CHANNEL, INWARDLY RECTIFYING, SUBFAMILY J, MEMBER 3) - GALLUS GALLUS (CHICKEN).
IRK3_HUMAN G PROTEIN-ACTIVATED INWARD RECTIFIER POTASSIUM CHANNEL 1 (GIRK1) (POTASSIUM CHANNEL, INWARDLY RECTIFYING, SUBFAMILY J, MEMBER 3) (KIR3.1) - HOMO SAPIENS (HUMAN).
IRK3_MOUSE G PROTEIN-ACTIVATED INWARD RECTIFIER POTASSIUM CHANNEL 1 (GIRK1) (POTASSIUM CHANNEL, INWARDLY RECTIFYING, SUBFAMILY J, MEMBER 3) (KGA) (KGB1) (KIR3.1) - MUS MUSCULUS (MOUSE), AND RATTUS NORVEGICUS (RAT).
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