| Literature References | 1. MILLER, C.
An overview of the potassium channel family.
GENOME BIOL. 1(4) 1-5 (2000).
2. BAHRING, R., MILLIGAN, C.J., VARDANYAN, V., ENGELAND, B., YOUNG, B.A.,
DANNENBERG, J., WALDSCHUTZ, R., EDWARDS, J.P., WRAY, D. AND PONGS, O.
Coupling of voltage-dependent potassium channel inactivation and
oxidoreductase active site of Kvbeta subunits.
J.BIOL.CHEM. 276 22923-22929 (2001).
3. LEICHER, T., BAHRING, R., ISBRANDT, D. AND PONGS, O.
Coexpression of the KCNA3B gene product with Kv1.5 Leads to a novel A-type
potassium channel.
J.BIOL.CHEM. 273 35095-35101 (1998).
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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].
Some types of K+ channel are closed at the resting potential of the cell,
but open on membrane depolarisation, and are thus known as voltage-gated
channels. Each of these types of channel typically comprises 4 pore-forming
alpha subunits that may associate with one of a number of different types of
beta subunit. Two types of beta subunit (KCNE and KCNAB) are presently known
to associate with voltage-gated alpha subunits (Kv, KCNQ and eag-like).
However, not all combinations of alpha and beta subunits are possible.
The KCNAB family of K+ channel beta subunits form tetramers arranged in
a similar manner to the pore forming alpha subunits. KCNAB subunits are
oxidoreductase enzymes, complete with nicotinamide (NADPH)-cofactors in
their active sites. Changes in the oxidoreductase activity appear to
markedly influence the gating mode of Kv channels, since mutations to the
catalytic residues in the active site lessen the inactivating activity of
KCNAB [2]. The KCNAB family is further divided into 3 subfamilies: KCNAB1
(Kvbeta3), KCNAB2 (Kvbeta2) and KCNAB3.
KCNAB3 associates with Kv1.5 alpha subunits, resulting in a much faster
inactivation than is observed in kv1.5 channels formed from alpha subunits
alone [3]. KCNAB3 channels are expressed specifically in the brain, with
most prominent expression in the cerebellum. Weaker expression is observed
in the cortex, occipital lobe, frontal lobe and temporal lobe.
KCNAB3CHANEL is a 4-element fingerprint that provides a signature for the
KCNAB voltage-gated K+ channel beta-3 subunit. The fingerprint was derived
from an initial alignment of 3 sequences: the motifs were drawn from
conserved regions spanning the C-terminal portion of the alignment. A
single iteration on SPTR39.22_17.3f was required to reach convergence, no
further sequences being identified beyond the starting set.
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