Kv6
The sparsely populated Kv channel subfamilies Kv5 and Kv6 each contain one member, Kv5.1 and Kv6.1 (see Chandy, K.G. and Gutman, G.A. (1995) In: (R.A. North, ed.), Handbook of Receptors and Channels. Ligand- and Voltage- Gated Ion Channels. CRC Press, Ann Arbor, MI, pp. 1-71) referred to as IK8 and K13, [399]. No function has yet been demonstrated for either of these proteins alone [399].
Kv channels are composed of four subunits that surround the central ion permeation pathway [664]:. Each subunit has six transmembrane domains (S1–S6) and a pore region containing the signature sequence GYG character- istic for potassium channels [667], [619]. Post-translational assembly of tetrameric Kv channels takes place in the ER2 membrane; sub- sequently the channels traffic to the plasma membrane [619], [668]. A highly conserved sequence in the cytoplasmic N terminus of Kv channels, the tetramerization domain or T1 domain, has been shown to play an important role in channel assembly [619], [669]. The T1 domain contains some of the molecular determinants for subfamily-specific homo- or heterotetrameric assembly of Kv alpha-subunits [669], [660],[598], [670]. The most striking difference between the T1 domains of Kv1 (Shaker) and Kv2–4 (non-Shaker) channels is the presence of intersubunit-coordinated Zn2+ ions at the assembly interface in non-Shaker channels. The Zn2+ ions are coordinated by a C3H1 motif embedded in a conserved sequence motif (HX5CX20CC) of the T1 domain, which is located near the distal end of the N terminus [671], [672], [673]. These four amino acids are exposed on the subunit interface, with one histidine and two cysteine residues belonging to one subunit and one cysteine residue belonging to the neighboring subunit [671]. The T1 domain facilitates tetrameric assembly of Kv channels. Kv subunits in which the T1 has been deleted have been reported to assemble in a promiscuous way via their transmembrane domains and to form stable, functional channels, but both the rates and the efficiency of channel assembly are significantly lower in the mutant channels as compared with their wild-type counterparts [668], [674]. Heteromeric assembly of channel subunits is a potential source of diversity of K+ channel properties.
References
Post MA
et al.
Kv2.1 and electrically silent Kv6.1 potassium channel subunits combine and express a novel current.
FEBS Lett.,
1996
Dec
9
, 399 (177-82).
Li M
et al.
Specification of subunit assembly by the hydrophilic amino-terminal domain of the Shaker potassium channel.
Science,
1992
Aug
28
, 257 (1225-30).
Lu J
et al.
T1-T1 interactions occur in ER membranes while nascent Kv peptides are still attached to ribosomes.
Biochemistry,
2001
Sep
18
, 40 (10934-46).
Xu J
et al.
Assembly of voltage-gated potassium channels. Conserved hydrophilic motifs determine subfamily-specific interactions between the alpha-subunits.
J. Biol. Chem.,
1995
Oct
20
, 270 (24761-8).
Mederos Y Schnitzler M
et al.
Mutation of histidine 105 in the T1 domain of the potassium channel Kv2.1 disrupts heteromerization with Kv6.3 and Kv6.4.
J. Biol. Chem.,
2009
Feb
13
, 284 (4695-704).
Barry DM
et al.
Myocardial potassium channels: electrophysiological and molecular diversity.
Annu. Rev. Physiol.,
1996
, 58 (363-94).
Robinson JM
et al.
Coupled tertiary folding and oligomerization of the T1 domain of Kv channels.
Neuron,
2005
Jan
20
, 45 (223-32).
Bixby KA
et al.
Zn2+-binding and molecular determinants of tetramerization in voltage-gated K+ channels.
Nat. Struct. Biol.,
1999
Jan
, 6 (38-43).
Jahng AW
et al.
Zinc mediates assembly of the T1 domain of the voltage-gated K channel 4.2.
J. Biol. Chem.,
2002
Dec
6
, 277 (47885-90).
Strang C
et al.
The role of Zn2+ in Shal voltage-gated potassium channel formation.
J. Biol. Chem.,
2003
Aug
15
, 278 (31361-71).
Tu L
et al.
Voltage-gated K+ channels contain multiple intersubunit association sites.
J. Biol. Chem.,
1996
Aug
2
, 271 (18904-11).
Credits
To cite this page: [Contributors] Channelpedia https://channelpedia.epfl.ch/wikipages/197/ , accessed on 2024 Dec 12