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PDBsum entry 1j7o
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Metal binding protein
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PDB id
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1j7o
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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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Solution structure of ca(2+)-Calmodulin reveals flexible hand-Like properties of its domains.
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Authors
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J.J.Chou,
S.Li,
C.B.Klee,
A.Bax.
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Ref.
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Nat Struct Biol, 2001,
8,
990-997.
[DOI no: ]
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PubMed id
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Abstract
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The solution structure of Ca(2+)-ligated calmodulin is determined from residual
dipolar couplings measured in a liquid crystalline medium and from a large
number of heteronuclear J couplings for defining side chains. Although the
C-terminal domain solution structure is similar to the X-ray crystal structure,
the EF hands of the N-terminal domain are considerably less open. The
substantial differences in interhelical angles correspond to negligible changes
in short interproton distances and, therefore, cannot be identified by
comparison of NOEs and X-ray data. NOE analysis, however, excludes a two-state
equilibrium in which the closed apo conformation is partially populated in the
Ca(2+)-ligated state. The difference between the crystal and solution structures
of Ca(2+)-calmodulin indicates considerable backbone plasticity within the
domains of calmodulin, which is key to their ability to bind a wide range of
targets. In contrast, the vast majority of side chains making up the target
binding surface are locked into the same chi(1) rotameric states as in complexes
with target peptide.
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Figure 3.
Figure 3. Normalized average difference,  D,
between the measured dipolar couplings and those predicted by
the refined NMR structure as a function of residue number.
 D
= ((( 1D[NH])2
+ ( 1D[C
 H
])2
+ ( 1D[C'C
])2
+ ( 1D[C'N])2
+ ( 2D[C'H
]
measure and best-fit couplings, where all couplings have been
normalized relative to 1D[NH]. No couplings were measured for
Asn 42 because residue 43 is a Pro and Asn 42 HN is broadened by
rapid solvent exchange at pH 7.0. Residues Met 76 -Asp 81 are
highly flexible and excluded from the structure calculation. The
symbols correspond to apo CaM (square), parvalbumin (triangle)
and Ca^2+ -CaM (circle) starting structures.
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Figure 4.
Figure 4. Ribbon diagrams of the backbone of the Ca^2+ -CaM
solution structure, shown in red, and the 1 Å crystal structure
(1EXR) in blue. a, For the N-terminal domain, the
superposition is optimized for residues 29 -54 (helices II and
III), revealing the large difference in the orientation of helix
I (26°) and IV (22°). b, For the C-terminal domain, residues 102
-127 (helices VI and VII) are superimposed, showing much smaller
orientation differences of 15° and 10° for helix V and VIII,
respectively. c,d, Solution structures including side chains,
color coded according to their mobility as determined by 3J[CC]
and 3J[CN] couplings. Red indicates extensive rotameric  [1]
averaging; blue, single [1]
rotamers; and gray, residues with insufficient data for
accurately defining [1]
distributions. Eight Met residues (yellow) have unique [1]
angles but exhibit extensive [3]
averaging. Figures generated using MOLMOL49.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Biol
(2001,
8,
990-997)
copyright 2001.
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