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PR01451

Identifier
SKCHANNEL  [View Relations]  [View Alignment]  
Accession
PR01451
No. of Motifs
2
Creation Date
05-DEC-2000
Title
Calcium-activated SK potassium channel signature
Database References
PRINTS; PR00169 KCHANNEL
Literature References
1. MILLER, C.
An overview of the potassium channel family.
GENOME BIOL. 1(4) 1-5 (2000).
 
2. ASHCROFT, F.M.
Ca2+-activated K+ channels.
IN ION CHANNELS AND DISEASE, ACADEMIC PRESS, 2000, PP.125-133.
 
3. VERGARA, C., LATORRE, R., MARRION, N.V. AND ADELMAN, J.P.
Calcium-activated potassium channels.
CURR.OPIN.NEUROBIOL. 8(3) 321-329 (1998).
 
4. ISHII, T.M., MAYLIE, J. AND ADELMAN, J.P.
Determinants of apamin and d-tubocurarine block in SK potassium channels.
J.BIOL.CHEM. 272(37) 23195-23200 (1997).
 
5. BOND, C.T., MAYLIE, J. AND ADELMAN, J.P.
Small-conductance calcium-activated potassium channels.
ANN.N.Y.ACAD.SCI. 868 370-378 (1999).
 
6. CASTLE, N.A.
Recent advances in the biology of small-conductance calcium-activated
potassium channels.
PERSPECTIVES DRUG DISCOVERY DESIGN 16 131-154 (1999).

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, calcium (Ca2+) activated 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+ channel (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].
 
Ca2+-activated K+ channels are a diverse group of channels that are
activated by an increase in intracellular Ca2+ concentration. They are
found in the majority of nerve cells, where they modulate cell excitability
and action potential. Three types of Ca2+-activated K+ channel have been
characterised, termed small-conductance (SK), intermediate conductance (IK)
and large conductance (BK) respectively [2-3].
 
SK channels are thought to play an important role in the functioning of
all excitable tissues. To date, 3 subtypes (designated SK1-SK3) have been
cloned, each of which possesses a different tissue expression profile: SK1
channels are expressed in the heart; SK2 channels are found in the adrenal
gland; and SK3 channels are known to be present in skeletal muscle.
 
Although SK channels have been classified as belonging to the 6TM domain
voltage-gated K+ channel family, they show little or no sequence similarity
to other family members. The fourth TM domain resembles the S4 voltage
sensor domain of Kv channels, since it contains 3 positively charged 
residues. However, despite similarity to the Kv voltage-sensory motif, SK 
channel activation is not voltage sensitive.
 
SKCHANNEL is a 2-element fingerprint that provides a signature for the
calcium-activated SK potassium channels. The fingerprint was derived from 
an initial alignment of 2 sequences: the motifs were drawn from conserved
regions within the N-terminal portion of the alignment, focusing on those
sections that characterise the SK potassium channels but distinguish them
from other members of the K+ channel superfamily. Three iterations on
SPTR39_14f were required to reach convergence, at which point a true set
comprising 7 sequences was identified.
Summary Information
7 codes involving  2 elements
Composite Feature Index
277
12
True Positives
O43517        P70604        P70605        P70606        
Q92952 Q9PTS9 Q9UGI6
Sequence Titles
O43517      CALCIUM-ACTIVATED POTASSIUM CHANNEL - Homo sapiens (Human). 
P70604 CALCIUM-ACTIVATED POTASSIUM CHANNEL RSK2 - Rattus norvegicus (Rat).
P70605 CALCIUM-ACTIVATED POTASSIUM CHANNEL RSK3 - Rattus norvegicus (Rat).
P70606 CALCIUM-ACTIVATED POTASSIUM CHANNEL RSK1 - Rattus norvegicus (Rat).
Q92952 CALCIUM-ACTIVATED POTASSIUM CHANNEL HSK1 - Homo sapiens (Human).
Q9PTS9 SMALL-CONDUCTANCE CALCIUM-ACTIVATED POTASSIUM CHANNEL - Gallus gallus (Chicken).
Q9UGI6 SK3 PROTEIN - Homo sapiens (Human).
Scan History
SPTR39_14f 3  100  NSINGLE    
Initial Motifs
Motif 1  width=21
Element Seqn Id St Int Rpt
KLGHRRALFEKRKRLSDYALI P70604 121 121 -
RLGHRRALFEKRKRLSDYALI P70606 88 88 -

Motif 2 width=19
Element Seqn Id St Int Rpt
EILVCAIHPIPGNYTFTWT P70604 221 79 -
ELAVCAIHPVPGHYRFTWT P70606 188 79 -
Final Motifs
Motif 1  width=21
Element Seqn Id St Int Rpt
KLGHRRALFEKRKRLSDYALI P70605 270 270 -
KLGHRRALFEKRKRLSDYALI Q9UGI6 274 274 -
KLGHRRALFEKRKRLSDYALI P70604 121 121 -
KLGHRRALFEKRKRLSDYALI Q9PTS9 94 94 -
KLGHRRAPFEKRKRLSDYALI O43517 269 269 -
RLGHRRALFEKRKRLSDYALI P70606 88 88 -
RLGHRRALFEKRKRLSDYALI Q92952 110 110 -

Motif 2 width=19
Element Seqn Id St Int Rpt
EMLVCAIHPIPGEYKFFWT P70605 370 79 -
EMLVCAIHPIPGEYKFFWT Q9UGI6 374 79 -
EILVCAIHPIPGNYTFTWT P70604 221 79 -
EILVCAIHPIPGNYTFTWT Q9PTS9 194 79 -
EMLVCAIHPIPGEYKFFWT O43517 369 79 -
ELAVCAIHPVPGHYRFTWT P70606 188 79 -
ELAVCAIHPVPGHYRFTWT Q92952 210 79 -