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PDBsum entry 3b8e
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Hydrolase/transport protein
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PDB id
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3b8e
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References listed in PDB file
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Key reference
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Title
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Crystal structure of the sodium-Potassium pump.
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Authors
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J.P.Morth,
B.P.Pedersen,
M.S.Toustrup-Jensen,
T.L.Sørensen,
J.Petersen,
J.P.Andersen,
B.Vilsen,
P.Nissen.
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Ref.
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Nature, 2007,
450,
1043-1049.
[DOI no: ]
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PubMed id
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Abstract
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The Na+,K+-ATPase generates electrochemical gradients for sodium and potassium
that are vital to animal cells, exchanging three sodium ions for two potassium
ions across the plasma membrane during each cycle of ATP hydrolysis. Here we
present the X-ray crystal structure at 3.5 A resolution of the pig renal
Na+,K+-ATPase with two rubidium ions bound (as potassium congeners) in an
occluded state in the transmembrane part of the alpha-subunit. Several of the
residues forming the cavity for rubidium/potassium occlusion in the
Na+,K+-ATPase are homologous to those binding calcium in the Ca2+-ATPase of
sarco(endo)plasmic reticulum. The beta- and gamma-subunits specific to the
Na+,K+-ATPase are associated with transmembrane helices alphaM7/alphaM10 and
alphaM9, respectively. The gamma-subunit corresponds to a fragment of the V-type
ATPase c subunit. The carboxy terminus of the alpha-subunit is contained within
a pocket between transmembrane helices and seems to be a novel regulatory
element controlling sodium affinity, possibly influenced by the membrane
potential.
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Figure 1.
Figure 1: Functional characterization of Na^+,K^+-ATPase used
for crystallization. a, The reaction cycle of the
Na^+,K^+-ATPase^2, ^3 showing in red the form crystallized. b,
Demonstration of ^86Rb^+ occlusion in the MgF[4]^2--bound form
of the pig renal Na^+,K^+-ATPase from outer medulla. The
dissociation of ^86Rb^+ from membranous enzyme pre-incubated
with ^86Rb^+ in the absence (lowest panel) or presence (middle
panel) of MgF[4]^2-, and from C[12]E[8]-solubilized enzyme
preincubated in the presence of MgF[4]^2- (uppermost panel), was
followed at 25 °C. Error bars, s.e.m.; n = 3.
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Figure 3.
Figure 3: Architecture of the Na^+,K^+-ATPase alpha- beta- bold
gamma- complex
and the K^+/Rb^+ sites. The cytoplasmic side is up in all
panels. a, The  -,
 -
and  -subunits
are coloured blue, wheat and red, respectively. Helices are
represented by cylinders and -strands
by arrows. The -ectodomain
is shown by surface representation of the experimental electron
density. The transmembrane segments of the -subunit
are numbered (yellow) starting with the most N-terminal. The
small C-terminal helix (S, for switch) is light red. Mg^2+,
MgF[4]^2- and Rb^+ ions are grey, orange and pink, respectively.
b, The red mesh (anomalous difference Fourier map) and the green
mesh (omit F[O]-F[C] electron density map) show the positions of
Rb^+ and K^+ ions, respectively. Oxygen-containing side chains
within and close to the coordination sphere are shown. c,
Structural alignment of the Na^+,K^+-ATPase (blue) with SERCA
(yellow; PDB 1WPG) in the E2⋅MgF[4]^2- forms. Yellow and
magenta spheres represent water molecules in SERCA and K^+/Rb^+
ions in Na^+,K^+-ATPase, respectively. d, Interaction between
Glu 327 ( M4)
and Leu 97 ( M1)^17.
The cyan mesh indicates the electron-density map (2F[O]-F[C]) of
M1
contoured at 1.0  .
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nature
(2007,
450,
1043-1049)
copyright 2007.
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