The Kir3.1 gene contains three exons separated by two introns, and its total length exceeds 45
kb. The two transmembrane domains, pore region, and
part of the putative carboxyl terminus are encoded by
exon 1, whereas the remainder of the tail is encoded
by exons 2 and 3. The mRNA transcription initiation
site was established, and the first 1520 bp upstream
were sequenced; this region lacked a traditional TATA
or CAAT box, but contained a GC-rich region as well
as various putative transcription factor-binding elements. The 1520 bp upstream and 84 bp downstream
of the transcription initiation site were tested for promoter activity in GH4-C1 cells. This sequence of 1604
bp contains a number of fragments that either stimulate or repress transcription, as tested by transient
expression of various Kir3.1 promoter/luciferase fusion gene constructs in GH4-C1 cells. Schoots 1997 
Kcnj3 : potassium inwardly-rectifying channel, subfamily J, member 3
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.
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.
The external part of the cell wall and/or plasma membrane.
external side of plasma membrane
The side of the plasma membrane that is opposite to the side that faces the cytoplasm.
Invagination of the plasma membrane of a muscle cell that extends inward from the cell surface around each myofibril. The ends of T-tubules make contact with the sarcoplasmic reticulum membrane.
A protein complex that possesses 6-phosphofructokinase activity; homodimeric, homooctameric, and allosteric homotetrameric forms are known.
Kir3 channels are activated following stimulation of G
protein-coupled receptors (GPCRs) that use the Gi/o
family of G proteins. Stimulation of the GPCR promotes
exchange of GDP for GTP on the Gα subunit which, in
turn, leads to activation of the Gα subunit and the Gβγ
dimer. Gβγ dimers bind to and activate Kir3 channels
(Reuveny et al. 1994 ; Wickman et al. 1994 ; Huang et al.
1995 ). Gα subunits are required for terminating Kir3
activation. The intrinsic GTPase activity of the Gα subunit
hydrolyses GTP, leading to inactivation of the Gβγ dimer.
Regulator of G protein signalling (RGS) proteins accelerate
the GTPase activity of Gα subunits (GAP), leading to faster
activation and deactivation of Kir3 channels (Doupnik
et al. 1997 ). (From Fowler )
Heterotetramers with other kir3
The Kir3 family consists of the Kir3.1, Kir3.2, Kir3.3, and Kir3.4 subunits, and the majority of functional Kir3 channels are believed to exist as heterotetram- ers containing the Kir3.1 subunit, although some studies report on functional Kir3.2 homomers and Kir3.2/3.3 combinations (Wischmeyer et al., 1997; Inanobe et al., 1999; Jelacic et al., 2000).
Constitutive and agonist-induced
interactions between Kir3 channels and various Gβγ combinations
in living cells are reported by Riven .
Gβ1-4 can interact with Kir3.1 in the absence of Kir3.4. Gβ5 does not directly interact with the channel but can still be co-immunoprecipated as part of a larger complex.
Kir3.1 is expressed in cells of different
lineage, i.e., cardiac atrial myocytes as well as various
neuronal cell types. Currently no
human cell line is known to express the Kir3.1 channel.
Schoots 1997 
G protein-gated inwardly rectifying potassium (GIRK
or Kir3) channel activity is important for regulating
excitability in the heart and brain (Stanfield et al. 2002 ).
Kir3.1 channel is involved
in the TLR4-mediated (Toll-like receptor in immune system) signal at an early event by facilitating the recruitment of TLR4 into lipid raft. 
Single Channel Recording of GIRK1 in CHO cells
Coexpression of GIRKI and GIRK2 in oocytes and CHO cells produce channels that have macro- scopic and single channel characteristics similar to those de- scribed in central neurons. In contrast, the single channel properties of either GIRK2 or CIR expressed alone are clearly different than any of the native inward rectifiers so far de- scribed. Additionally, GIRK1 does not appear to form func- tional homomeric channels in oocytes or mammalian cell lines, and probably does not form homomeric channels in vivo