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PDBsum entry 1cm4
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Calcium-binding/transferase
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PDB id
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1cm4
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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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Motions of calmodulin characterized using both bragg and diffuse X-Ray scattering.
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Authors
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M.E.Wall,
J.B.Clarage,
G.N.Phillips.
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Ref.
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Structure, 1997,
5,
1599-1612.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: Calmodulin is a calcium-activated regulatory protein which can bind
to many different targets. The protein resembles a highly flexible dumbbell, and
bends in the middle as it binds. This and other motions must be understood to
formulate a realistic model of calmodulin function. RESULTS: Using the Bragg
reflections from X-ray crystallography, a multiple-conformer refinement of a
calmodulin-peptide complex shows anisotropic displacements, with high variations
of dihedral angles in several nonhelical domains: the flexible linker; three of
the four calcium-binding sites (including both of the N-terminal sites); and a
turn connecting the C-terminal EF-hand calcium-binding domains.
Three-dimensional maps of the large scale diffuse X-ray scattering data show
isotropic liquid-like motions with an unusually small correlation length.
Three-dimensional maps of the small scale diffuse streaks show highly coupled,
anisotropic motions along the head-to-tail molecular packing direction in the
unit cell. There is also weak coupling perpendicular to the head-to-tail packing
direction, particularly across a cavity occupied by the disordered linker domain
of the molecule. CONCLUSIONS: Together, the Bragg and diffuse scattering present
a self-consistent description of the motions in the flexible linker of
calmodulin. The other mobile regions of the protein are also of great interest.
In particular, the high variations in the calcium-binding sites are likely to
influence how strongly they bind ions. This is especially important in the
N-terminal sites, which regulate the activity of the molecule.
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Figure 1.
Figure 1. Dynamics in calmodulin binding. The linker of
calmodulin (white) bends as the ends of the protein engulf the
target (red stick model); there are also significant motions
within the globular ends. Experiments to characterize these
motions are necessary to understand how calmodulin works (see
text for details). Within the globular ends, helices are shown
in cyan, b strands in green and loops in orange; Ca^2+ ions are
depicted as white spheres. (The figure was made using the
program RIBBONS [41].)
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The above figure is
reprinted
by permission from Cell Press:
Structure
(1997,
5,
1599-1612)
copyright 1997.
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Secondary reference #1
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Title
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Modulation of calmodulin plasticity in molecular recognition on the basis of X-Ray structures.
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Authors
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W.E.Meador,
A.R.Means,
F.A.Quiocho.
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Ref.
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Science, 1993,
262,
1718-1721.
[DOI no: ]
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PubMed id
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Secondary reference #2
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Title
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Target enzyme recognition by calmodulin: 2.4 a structure of a calmodulin-Peptide complex.
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Authors
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W.E.Meador,
A.R.Means,
F.A.Quiocho.
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Ref.
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Science, 1992,
257,
1251-1255.
[DOI no: ]
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PubMed id
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