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PDBsum entry 2vaf
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Metal binding protein
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PDB id
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2vaf
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References listed in PDB file
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Key reference
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Title
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Characterization of human cardiac calsequestrin and its deleterious mutants.
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Authors
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E.Kim,
B.Youn,
L.Kemper,
C.Campbell,
H.Milting,
M.Varsanyi,
C.Kang.
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Ref.
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J Mol Biol, 2007,
373,
1047-1057.
[DOI no: ]
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PubMed id
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Abstract
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Mutations of conserved residues of human cardiac calsequestrin (hCSQ2), a
high-capacity, low-affinity Ca2+-binding protein in the sarcoplasmic reticulum,
have been associated with catecholamine-induced polymorphic ventricular
tachycardia (CPVT). In order to understand the molecular mechanism and
pathophysiological link between these CPVT-related missense mutations of hCSQ2
and the resulting arrhythmias, we generated three CPVT-causing mutants of hCSQ2
(R33Q, L167H, and D307H) and two non-pathological mutants (T66A and V76M) and
investigated the effect of these mutations. In addition, we determined the
crystal structure of the corresponding wild-type hCSQ2 to gain insight into the
structural effects of those mutations. Our data show clearly that all three
CPVT-related mutations lead to significant reduction in Ca2+-binding capacity in
spite of the similarity of their secondary structures to that of the wild-type
hCSQ2. Light-scattering experiments indicate that the Ca2+-dependent
monomer-polymer transitions of the mutants are quite different, confirming that
the linear polymerization behavior of CSQ is linked directly to its
high-capacity Ca2+ binding. R33Q and D307H mutations result in a monomer that
appears to be unable to form a properly oriented dimer. On the other hand, the
L167H mutant has a disrupted hydrophobic core in domain II, resulting in high
molecular aggregates, which cannot respond to Ca2+. Although one of the
non-pathological mutants, T66A, shares characteristics with the wild-type, the
other null mutant, V76M, shows significantly altered Ca2+-binding and
polymerization behaviors, calling for careful reconsideration of its status.
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Figure 1.
Figure 1. A diagram of CSQ polymerization. The CSQ molecule
exists as either a monomer or a wide range of high molecular
mass clusters, depending on the ionic environment. The extended
N terminus of CSQ establishes the front-to-front dimer interface
through arm exchange. Following a further increase of the
concentration of Ca^2+, the carboxy terminus of CSQ, which is
the most negative region, forms tetramer and higher-order linear
polymers capturing substantial amounts of Ca^2+ in the
back-to-back interface.
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Figure 7.
Figure 7. Amino acid sequence comparison of human CSQ1 with
human, canine, rabbit, chicken and xenopus CSQ2. Five mutational
sites (R33, T66, V76, L167, and D307) are highlighted in green
and the mutation was named according to the amino acid number in
the unprocessed CSQ. The signal peptides are indicated with the
black broken-line box. The secondary structural elements are
indicated with colored arrows on top of the corresponding
sequences and each domain (I, II and III) is marked with green
lines.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2007,
373,
1047-1057)
copyright 2007.
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