| Literature References | 1. MILLER, C.
An overview of the potassium channel family.
GENOME BIOL. 1(4) 1-5 (2000).
2. ASHCROFT, F.M.
Voltage-gated K+ channels.
IN ION CHANNELS AND DISEASE, ACADEMIC PRESS, 2000, PP.97-123.
3. SANSOM, M.S.
Putting the parts together.
CURR.BIOL. 9(19) R738-R741 (1999).
4. SALINAS, M., DUPRAT, F., HEURTEAUX, C., HUGNOT, J-P. AND LAZDUNSKI, M.
New modulatory alpha subunits for mammalian shab K+ channels.
J.BIOL.CHEM. 272(39) 24371-24379 (1997).
5. SHEPARD, A.R. AND RAE, J.L.
Electrically silent potassium channel subunits from human lens epithelium.
AM.J.PHYSIOL. 277 C412-C424 (1999).
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| Documentation | Potassium ion (K+) channels are a structurally diverse group of proteins
that facilitate the flow of K+ ions across cell membranes. They are
ubiquitous, being present in virtually all cell types. Activation of K+
channels tends to hyperpolarise cells, reducing the membrane's electrical
resistance, dampening nervous activity. In eukaryotic cells, K+ channels
are involved in neural signalling and generation of the cardiac rhythm, and
act as effectors in signal transduction pathways involving G protein-
coupled receptors (GPCRs). In prokaryotic cells, they play a role in the
maintenance of ionic homeostasis [1].
Structurally, Kv channels belong to the subfamily of K+ channels whose
subunits contain 6 transmembrane (TM) domains: these are the voltage-
gated K+ (Kv) channels, the KCNQ channels, the EAG-like K+ channels and
3 kinds of Ca2+-activated K+ channels (BK, IK and SK) [2]. All K+
channels share a characteristic sequence feature: a TMxTVGYG motif
that resides between the 2 C-terminal membrane spanning helices, and
forms the K+-selective pore domain [1-2].
The Kv family can be divided into 4 subfamilies on the basis of sequence
similarity and function: Shaker (Kv1), Shab (Kv2), Shaw (Kv3) and Shal
(Kv4). All consist of pore-forming alpha subunits that associate with
different types of beta subunit. To form a functional K+ channel pore,
4 alpha subunits and 4 beta subunits are required. The alpha subunits
have 6 well-conserved TM domains, a pore loop region and variable length
N- and C-termini. TM domains 5/6 and the loop region form the K+
channel pore through which the K+ ions pass [3].
More recently, 4 new electrically-silent alpha subunits have been cloned:
Kv5 (KCNF), Kv6 (KCNG), Kv8 and Kv9 (KCNS). These subunits do not themselves
possess any functional activity, but appear to form heteromeric channels
with Kv2 subunits, and thus modulate Shab channel activity [4]. When highly
expressed, they inhibit channel activity, but at lower levels show more
specific modulatory actions. Coexpression of Kv9 subunits with Shab subunits
produces a shift in the voltage-dependence of channel inactivation toward
more negative potentials [4]. In addition, Shab channel deactivation and
inactivation are slowed, and the single channel conductance is increased [5].
KV9CHANNEL is a 7-element fingerprint that provides a signature for the Kv9
potassium channel alpha subunits. The fingerprint was derived from an
initial alignment of 6 sequences: the motifs were drawn from conserved
regions spanning virtually the full alignment length - motifs 1-5 reside
within the N-terminal cytoplasmic domain; motif 6 spans TM domain 1; and
motif 7 encodes TM domain 6. Two iterations on SPTR39_15f were required to
reach convergence, at which point a true set comprising 8 sequences was
identified.
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| Sequence Titles | O35173 K+ VOLTAGE-GATED CHANNEL, SUBFAMILY S, 1 (POTASSIUM CHANNEL ALPHA SUBUNIT) - Mus musculus (Mouse).
O35174 K+ VOLTAGE-GATED CHANNEL, SUBFAMILY S, 2 (POTASSIUM CHANNEL ALPHA SUBUNIT) - Mus musculus (Mouse).
O43651 SHAB-RELATED DELAYED-RECTIFIER K+ CHANNEL ALPHA SUBUNIT - Homo sapiens (Human).
O43652 DELAYED-RECTIFIER K+ CHANNEL ALPHA SUBUNIT - Homo sapiens (Human).
O54900 SHAB-RELATED DELAYED-RECTIFIER K+ CHANNEL - Rattus norvegicus (Rat).
O88758 POTASSIUM CHANNEL, ALPHA SUBUNIT - Rattus norvegicus (Rat).
O88759 POTASSIUM CHANNEL, ALPHA SUBUNIT - Rattus norvegicus (Rat).
Q9TT17 VOLTAGE-GATED DELAYED-RECTIFIER POTASSIUM CHANNEL KV9.3 - Oryctolagus cuniculus (Rabbit).
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