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PDBsum entry 1t5t
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Contents |
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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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Phosphoryl transfer and calcium ion occlusion in the calcium pump.
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Authors
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T.L.Sørensen,
J.V.Møller,
P.Nissen.
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Ref.
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Science, 2004,
304,
1672-1675.
[DOI no: ]
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PubMed id
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Abstract
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A tight coupling between adenosine triphosphate (ATP) hydrolysis and vectorial
ion transport has to be maintained by ATP-consuming ion pumps. We report two
crystal structures of Ca2+-bound sarco(endo)plasmic reticulum Ca2+-adenosine
triphosphatase (SERCA) at 2.6 and 2.9 angstrom resolution in complex with (i) a
nonhydrolyzable ATP analog [adenosine (beta-gamma methylene)-triphosphate] and
(ii) adenosine diphosphate plus aluminum fluoride. SERCA reacts with ATP by an
associative mechanism mediated by two Mg2+ ions to form an
aspartyl-phosphorylated intermediate state (Ca2-E1 approximately P). The
conformational changes that accompany the reaction with ATP pull the
transmembrane helices 1 and 2 and close a cytosolic entrance for Ca2+, thereby
preventing backflow before Ca2+ is released on the other side of the membrane.
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Figure 2.
Fig. 2. Conformational changes upon nucleotide binding.
Comparison of the Ca[2]-E[1] and Ca[2]-E[1]-AMPPCP forms, based
on the same alignment as in Fig. 1C. Domains occupying similar
positions are shown as colored surfaces with the coordination
spheres of the two calcium ions in blue. The series of
conformational changes leading from ATP binding to Ca^2+
occlusion have been indicated by arrows on the Ca[2]-E[1] form.
The figure was prepared with PyMOL (26).
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Figure 3.
Fig. 3. The Mg2+-catalyzed phosphoryl transferase activity. (A)
Overview of Mg: AMPPCP binding, shown with a ball-and-stick
representation of interacting residues. The color scheme is the
same as in Fig. 1C. The bent conformation of the nucleotide,
stabilized primarily by three arginines, can be seen. (B)
Coordination of the  -phosphate and
Asp351 by a magnesium ion. The Asp351 side chain is still far
from the -phosphorus atom.
(C) The transition state of phosphoryl transfer as mimicked by
ADP:AlF[4]^-. The Mg2+ ion coordinates Asp351 and AlF[4]^-, and
the ß-phosphate and the Asp351 side chain form tight
coordination of the aluminum atom as indicated by dashed lines
in color. Residues important for stabilization are indicated.
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The above figures are
reprinted
by permission from the AAAs:
Science
(2004,
304,
1672-1675)
copyright 2004.
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