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PR01585

Identifier
TASK3CHANNEL  [View Relations]  [View Alignment]  
Accession
PR01585
No. of Motifs
4
Creation Date
10-SEP-2001
Title
TASK-3 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. KIM, Y., BANG, H. AND KIM, D.
TASK-3, a new member of the tandem pore K+ channel family.
J.BIOL.CHEM. 275(13) 9340-9347 (2000).
 
9. RAJAN, S., WISCHMEYER, E., XIN LUI, G., PREISIG-MULLER, R., DAUT, J.,
KARSCHIN, A. AND DERST, C.
TASK-3, a novel tandem pore-domain acid-sensitive K+ channel: an
extracellular histidine as pH sensor.
J.BIOL.CHEM. 275 16650-16657 (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 subunits 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] was
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-3 was first cloned from rat and has been subsequently cloned from human
and guinea pig. It is expressed in many tissues, especially the brain. It
is involved in setting the membrane potential as well as action potential 
duration in certain neurons. It is closed at pH6.6: the histidine residue
at position 98 located near a `GYG' motif in the first P-domain is thought
to confer the extracellular pH sensitivity [8].
 
TASK3CHANNEL is a 4-element fingerprint that provides a signature for the
TASK-3 K+ channel. The fingerprint was derived from 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 
TASK-3 channel proteins but distinguish them from related TASK family
members - motifs 1 and 2 span the first putative TM domain; and motifs 3
and 4 are situated in the C-terminus. A single iteration on SPTR39.22_17.3f 
was required to reach convergence, no further sequences being identified
beyond the starting set.
Summary Information
3 codes involving  4 elements
0 codes involving 3 elements
0 codes involving 2 elements
Composite Feature Index
43333
30000
20000
1234
True Positives
CIW9_CAVPO    CIW9_HUMAN    Q9JLD4        
Sequence Titles
CIW9_CAVPO  POTASSIUM CHANNEL SUBFAMILY K MEMBER 9 (ACID-SENSITIVE POTASSIUM CHANNEL PROTEIN TASK-3) (TWIK-RELATED ACID-SENSITIVE K+ CHANNEL 3) - Cavia porcellus (Guinea pig). 
CIW9_HUMAN POTASSIUM CHANNEL SUBFAMILY K MEMBER 9 (ACID-SENSITIVE POTASSIUM CHANNEL PROTEIN TASK-3) (TWIK-RELATED ACID-SENSITIVE K+ CHANNEL 3) - Homo sapiens (Human).
Q9JLD4 POTASSIUM CHANNEL TASK3 - Rattus norvegicus (Rat).
Scan History
SPTR39.22_17.3f 1  300  NSINGLE    
Initial Motifs
Motif 1  width=16
Element Seqn Id St Int Rpt
DHEMREEEKLKAEEIR CIW9_CAVPO 32 32 -
DHEMREEEKLKAEEIR CIW9_HUMAN 32 32 -
DHEMREEEKLKAEEVR Q9JLD4 32 32 -

Motif 2 width=13
Element Seqn Id St Int Rpt
YNISTEDYRQLEL CIW9_CAVPO 52 4 -
YNISSEDYRQLEL CIW9_HUMAN 52 4 -
YNISSDDYQQLEL Q9JLD4 52 4 -

Motif 3 width=13
Element Seqn Id St Int Rpt
GNPSSVVTHISEE CIW9_CAVPO 266 201 -
GNRNSMVIHIPEE CIW9_HUMAN 266 201 -
GNPRRVVVRVPQS Q9JLD4 265 200 -

Motif 4 width=17
Element Seqn Id St Int Rpt
EEISPSTLKNSLFPSPI CIW9_CAVPO 326 47 -
EEISPSTLKNSLFPSPI CIW9_HUMAN 335 56 -
EEIPPDVLRNTYFRSPF Q9JLD4 356 78 -
Final Motifs
Motif 1  width=16
Element Seqn Id St Int Rpt
DHEMREEEKLKAEEIR CIW9_CAVPO 32 32 -
DHEMREEEKLKAEEIR CIW9_HUMAN 32 32 -
DHEMREEEKLKAEEVR Q9JLD4 32 32 -

Motif 2 width=13
Element Seqn Id St Int Rpt
YNISTEDYRQLEL CIW9_CAVPO 52 4 -
YNISSEDYRQLEL CIW9_HUMAN 52 4 -
YNISSDDYQQLEL Q9JLD4 52 4 -

Motif 3 width=13
Element Seqn Id St Int Rpt
GNPSSVVTHISEE CIW9_CAVPO 266 201 -
GNRNSMVIHIPEE CIW9_HUMAN 266 201 -
GNPRRVVVRVPQS Q9JLD4 265 200 -

Motif 4 width=17
Element Seqn Id St Int Rpt
EEISPSTLKNSLFPSPI CIW9_CAVPO 326 47 -
EEISPSTLKNSLFPSPI CIW9_HUMAN 335 56 -
EEIPPDVLRNTYFRSPF Q9JLD4 356 78 -