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PR01690

Identifier
TASK5CHANNEL  [View Relations]  [View Alignment]  
Accession
PR01690
No. of Motifs
4
Creation Date
13-MAR-2002
Title
TASK-5 K+ channel signature
Database References
PRINTS; PR00169 KCHANNEL; PR01333 2POREKCHANEL; PR01095 TASKCHANNEL
Literature References
1. KETCHUM, K.A., JOINER, W.J., SELLERS, A.J., KACZMAREK, L.K. AND
GOLDSTEIN, S.A.N.
A new family of outwardly rectifying potassium channel proteins with two
pore domains in tandem.
NATURE 376 690-695 (1995).
 
2. GOLDSTEIN, S.A.N., PRICE, L.A., ROSENTHAL, D.N. AND PAUSCH, M.H.
ORK1, a potassium-selective leak channel with two pore domains cloned from
Drosophila melanogaster by expression in Saccharomyces cerevisiae.
PROC.NATL.ACAD.SCI.U.S.A. 93 13256-13261 (1996).
 
3. FINK, M. DUPRAT, F., LESAGE, F., REYES, R., ROMEY, G., HEURTEAUX, C. AND
LAZDUNSKI, M.
Cloning, functional expression and brain localization of a novel
unconventional outward rectifier K+ channel.
EMBO J. 15 6854-6862 (1996).
 
4. LESAGE, F., GUILLEMARE, E., FINK, M., DUPRAT, F., LAZDUNSKI, M., ROMEY,
G. AND BARHANIN, J.
TWIK-1, a ubiquitous human weakly inward rectifying K+ channel with novel
structure.
EMBO J. 15 1004-1011 (1996).
 
5. DUPRAT, F., LESAGE, F., FINK, M., REYES, R., HEURTEAUX, C. AND
LAZDUNSKI, M.
TASK, a human background K+ channel to sense external pH variations near
physiological pH.
EMBO J. 16 5464-5471 (1997).
 
6. FINK, M., LESAGE, F., DUPRAT, F., HEURTEAUX, C., REYES, R., FOSSET, M.
AND LAZDUNSKI, M.
A neuronal two P domain K+ channel stimulated by arachidonic acid and
polyunsaturated fatty acids.
EMBO J. 17 3297-3308 (1998).
 
7. PATEL, A.J. AND HONORE, E.
Properties and modulation of mammalian 2P domain K+ channels.
TRENDS NEUROSCI. 24 (6) 339-346 (2001).
 
8. KARSCHIN, C., WISCHMEYER, E., PREISIG-MULLER, R., RAJAN, S., DERST, C.,
GRZESCHIK, K.H., DAUT. J. AND KARSCHIN, A.
Expression pattern in brain of TASK-1, TASK-3, and a tandem pore domain K(+)
gr; 
channel subunit, TASK-5, associated with the central auditory nervous
system.
MOL.CELL NEUROSCI. 18(6) 632-648 (2001).
 
9. ASHMOLE, I., GOODWIN, P.A. AND STANFIELD, P.R.
TASK-5, a novel member of the tandem pore K+ channel family.
PFLUGERS ARCH. 442(6) 828-833 (2000).

Documentation
Potassium (K+) channels play a key role in many cellular functions, in both
excitable and non-excitable tissues. Among the ion channels, they form the
largest family in terms of both structure and function. K+ channel subunits
contain a conserved pore-forming motif, the P-domain, which is considered to
be an essential element of the aqueous K+-selective pore. Shaker-type and
Kir K+ channel subunits both contain a single P-domain, and four such
subunits are thought to associate to form a multimer, together with
associated auxillary (regulatory) subunits. Recently, a new class of K+ 
channel subunit was cloned, which is clearly distinct from the Shaker and
Kir families; the new class contains not one but two P-domains in each
subunit, and evidence suggests a complete channel may be formed by the
dimerisation of two such subunits.
 
The first member of this family (TOK1) cloned from S.cerevisiae [1] is
predicted to have eight potential transmembrane (TM) helices. However,
subsequently-cloned two P-domain family members from Drosophila and
mammalian species are predicted to have only four TM segments. They are
usually referred to as TWIK-related channels (Tandem of P-domains in a 
Weakly Inward rectifying K+ channel) [2-6]. Functional characterisation of
these channels has revealed a diversity of properties in that they may show  
inward or outward rectification, their activity may be modulated in
different directions by protein phosphorylation, and their sensitivity to
changes in intracellular or extracellular pH varies. Despite these disparate 
properties, they are all thought to share the same topology of four TM 
segments, including two P-domains. That TWIK-related K+ channels all produce
instantaneous and non-inactivating K+ currents, which do not display a
voltage-dependent activation threshold, suggests that they are background
(leak) K+ channels involved in the generation and modulation of the resting
membrane potential in various cell types. Further studies have revealed that
they may be found in many species, including: plants, invertebrates and 
mammals.
 
The TASK (TWIK-related acid-sensitive K+ channel) family contains five
members (TASK1-5), which share no more than 54% amino acid identity. These
form functional K+ channels in various cell types and encode background
K+ channels, thereby helping to set the resting membrane potential. All
members are very sensitive to variations in extracellular pH in the
physiological range, changing from fully-open to closed in approximately
0.5pH units around pH7.4. Thus, they may well constitute biological sensors
of external pH variations [7].
 
TASK-5 is expressed in the pancreas, liver, kidney, lung, ovary, testis and
heart. It requires another as yet unidentified partner subunit to form 
functional channels in the plasma membrane, or it may form a channel in an
intracellular organelle [8,9].
 
TASK5CHANNEL is a 4-element fingerprint that provides a signature for the
TASK-5 K+ channel. The fingerprint was derived from an initial alignment of
2 sequences: the motifs were drawn from conserved regions spanning virtually
the full alignment length, focusing on those sections that characterise
TASK-5 proteins but distinguish them from related TASK family members -
motif 1 lies at the N-terminus; and motifs 2-4 span the C-terminus. A
single iteration on SPTR40_18f was required to reach convergence, no
further sequences being identified beyond the starting set.
Summary Information
2 codes involving  4 elements
0 codes involving 3 elements
0 codes involving 2 elements
Composite Feature Index
42222
30000
20000
1234
True Positives
Q9H427        Q9HBC8        
Sequence Titles
Q9H427      DJ781B1.1 (A NOVEL PROTEIN SIMILAR TO THE ACID-SENSITIVE POTASSIUM CHANNEL PROTEIN TASK (KCNK3)) - Homo sapiens (Human). 
Q9HBC8 TWO PORE POTASSIUM CHANNEL KT3.3 (TANDEM PORE DOMAIN POTASSIUM CHANNEL TASK-5) - Homo sapiens (Human).
Scan History
SPTR40_18f 1  200  NSINGLE    
Initial Motifs
Motif 1  width=18
Element Seqn Id St Int Rpt
FDALESEAESGRQRLLVQ Q9H427 26 26 -
FDALESEAESGRQRLLVQ Q9HBC8 26 26 -

Motif 2 width=16
Element Seqn Id St Int Rpt
RFLVASADWPERAART Q9H427 245 201 -
RFLVASADWPERAARP Q9HBC8 245 201 -

Motif 3 width=17
Element Seqn Id St Int Rpt
SVGSASVFCHVHKLERC Q9H427 283 22 -
SVGSASVFCHVHKLERC Q9HBC8 283 22 -

Motif 4 width=15
Element Seqn Id St Int Rpt
GFSPPSSPGVVRGGQ Q9H427 305 5 -
GFSPPSSPGVVRGGQ Q9HBC8 305 5 -
Final Motifs
Motif 1  width=18
Element Seqn Id St Int Rpt
FDALESEAESGRQRLLVQ Q9H427 26 26 -
FDALESEAESGRQRLLVQ Q9HBC8 26 26 -

Motif 2 width=16
Element Seqn Id St Int Rpt
RFLVASADWPERAART Q9H427 245 201 -
RFLVASADWPERAARP Q9HBC8 245 201 -

Motif 3 width=17
Element Seqn Id St Int Rpt
SVGSASVFCHVHKLERC Q9H427 283 22 -
SVGSASVFCHVHKLERC Q9HBC8 283 22 -

Motif 4 width=15
Element Seqn Id St Int Rpt
GFSPPSSPGVVRGGQ Q9H427 305 5 -
GFSPPSSPGVVRGGQ Q9HBC8 305 5 -