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PDBsum entry 2zd9
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Membrane protein
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PDB id
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2zd9
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References listed in PDB file
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Key reference
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Title
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Structure of the transmembrane regions of a bacterial cyclic nucleotide-Regulated channel.
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Authors
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G.M.Clayton,
S.Altieri,
L.Heginbotham,
V.M.Unger,
J.H.Morais-Cabral.
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Ref.
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Proc Natl Acad Sci U S A, 2008,
105,
1511-1515.
[DOI no: ]
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PubMed id
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Abstract
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The six-transmembrane helix (6 TM) tetrameric cation channels form the largest
ion channel family, some members of which are voltage-gated and others are not.
There are no reported channel structures to match the wealth of functional data
on the non-voltage-gated members. We determined the structure of the
transmembrane regions of the bacterial cyclic nucleotide-regulated channel
MlotiK1, a non-voltage-gated 6 TM channel. The structure showed how the S1-S4
domain and its associated linker can serve as a clamp to constrain the gate of
the pore and possibly function in concert with ligand-binding domains to
regulate the opening of the pore. The structure also led us to hypothesize a new
mechanism by which motions of the S6 inner helices can gate the ion conduction
pathway at a position along the pore closer to the selectivity filter than the
canonical helix bundle crossing.
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Figure 1.
Architecture of 6 TM channel. (A) Illustration of a 6 TM
channel. The ion pore regions (S5, Ploop, and S6) are shown in
red. Also shown are the S1–S4 domain and a C-terminal
cytoplasmic domain [CNB domain (CNBD)]. (B) MlotiK1 structure
viewed from the extracellular side. One subunit is shown in red.
TMs are labeled S1 to S6. Green spheres in the pore are K^+. (C)
Stereo side view of the MlotiK1 channel structure. Extracellular
side at the top of figure. Subunits are shown in different
colors. Some of the TMs and the S4–S5 linker are labeled. One
of the C termini is indicated by C.
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Figure 5.
The S4 helix. (A) Stereo side view of MlotiK1 and Kv1.2
S1–S4 domains superposed via S2 and S1. 3[10] regions in S4 of
MlotiK1 and Kv1.2 are shown in red and cyan, respectively. Other
TMs are represented by brown ribbons. S4 residues discussed in
the text are labeled. (B) Extracellular view of S1–S4 domains
from MlotiK1 and Kv1.2 superposed via S2 and S1. 3[10] regions
in S4 as in A. Other helical regions are in white ribbons. Kv1.2
R1, R2, R3, R4, K5, and R6 and equivalent MlotiK1 Cα atoms are
shown as blue and black spheres, respectively. (C) Surface
representation of MlotiK1 S1–S4 domain. S4 is shown as a red
ribbon, with residues equivalent to R2, R3, R4, K5, and R6 shown
as sticks. Protein regions from S1 to S3 are shown as gray
surface representations. S1, S2, and S3 helices are shown as
green ribbons inside the surface. (D) Same as in C but viewed
from the extracellular side.
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