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PDBsum entry 1s5h
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Membrane protein
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PDB id
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1s5h
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Contents |
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211 a.a.
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219 a.a.
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103 a.a.
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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A mutant kcsa k(+) channel with altered conduction properties and selectivity filter ion distribution.
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Authors
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M.Zhou,
R.Mackinnon.
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Ref.
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J Mol Biol, 2004,
338,
839-846.
[DOI no: ]
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PubMed id
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Abstract
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The selectivity filter of K(+) channels is comprised of a linear queue of four
equal-spaced ion-binding sites spanning a distance of 12A. Each site is formed
of eight oxygen atoms from the protein. The first three sites, numbered 1-3 from
the extracellular side, are made of exclusively main-chain carbonyl oxygen
atoms. The fourth site, closest to the intracellular side, is made of four
main-chain carbonyl oxygen atoms and four threonine side-chain hydroxyl oxygen
atoms. Here we characterize the effects of mutating the threonine to cysteine on
the distribution of ions in the selectivity filter and on the conduction of ions
through the filter. The mutation influences the occupancy of K(+) at sites 2 and
4 and it reduces the maximum rate of conduction in the limit of high K(+)
concentration. The mutation does not affect the conduction of Rb(+). These
results can be understood in the context of a conduction mechanism in which a
pair of K ions switch between energetically balanced 1,3 and 2,4 configurations.
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Figure 2.
Figure 2. A, Stereo view of the selectivity filter region
for the T75C mutant KcsA channel. The structure, solved in 200
mM K+, is shown with residues E71 to D80 (from two diagonally
opposed subunits) rendered in a ball-and-stick representation.
Green spheres represent K+ binding sites in the filter, and the
magenta sphere represents a site with residual electron density.
The 2F[o] -F[c] electron density map (contoured at 2s)
validating the structure is shown as a blue mesh. B, Stereo view
of the selectivity filter region for the wild-type KcsA. The
structure (PDB code 1K4C[3.]), solved in 200 mM K+, is
represented in the same way as in A. C, Stereo view of the
selectivity filter region of the T75C (red) superimposed on that
of the wild-type (blue).
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Figure 5.
Figure 5. Comparison of K+ and Rb^+ conduction properties
in the wild-type KcsA. Cord conductances (180 mV) are plotted
against either K+ or Rb^+ concentrations. The data in this
Figure are from Figure 3(A) of Morais-Cabral et al.[2.]
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2004,
338,
839-846)
copyright 2004.
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