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PDBsum entry 1avs
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Muscle contraction
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PDB id
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1avs
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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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Structural details of a calcium-Induced molecular switch: X-Ray crystallographic analysis of the calcium-Saturated n-Terminal domain of troponin c at 1.75 a resolution.
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Authors
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N.C.Strynadka,
M.Cherney,
A.R.Sielecki,
M.X.Li,
L.B.Smillie,
M.N.James.
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Ref.
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J Mol Biol, 1997,
273,
238-255.
[DOI no: ]
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PubMed id
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Abstract
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We have solved and refined the crystal and molecular structures of the
calcium-saturated N-terminal domain of troponin C (TnC) to 1.75 A resolution.
This has allowed for the first detailed analysis of the calcium binding sites of
this molecular switch in the calcium-loaded state. The results provide support
for the proposed binding order and qualitatively, for the affinity of calcium in
the two regulatory calcium binding sites. Based on a comparison with the
high-resolution apo-form of TnC we propose a possible mechanism for the
calcium-mediated exposure of a large hydrophobic surface that is central to the
initiation of muscle contraction within the cell.
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Figure 6.
Figure 6. The 12 residues of the EF-hand site I of N-TnC. In this and Figure 7, residues are color-coded according to
type: aliphatic hydrophobic are green; aromatic residues are brown; methionine are yellow; positively charged resi-
dues are blue; negatively charged residues are red and polar side-chains, Ser, Thr, Asn and Gln are orange and pink.
Main-chain atoms C
a
, C, D, N are depicted in white. Calcium is shown as a magenta sphere. Water molecules (five is
equatorial, nine is axial) are shown as cyan spheres. Water molecules are labelled as 5 or 9 depending on which
liganding position in the EF-hand loop they occupy. Hydrogen bonds are denoted as broken yellow lines. (a) Ligand-
ing residues in the 2-Ca
2+
form; (b) hydrogen bonding patterns within the 2-Ca
2+
form; (c) a similar view of site I in
the apo 0-Ca
2+
form of N-TnC. The Figure was generated using Raster 3D (Merrit & Murphy, 1994).
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Figure 7.
Figure 7. The 12 residues of the EF-hand site II of N-TnC. Calcium is shown as a magenta sphere. Water molecules
(water 9 is in the axial position) are shown as cyan spheres. Hydrogen bonds are denoted as broken yellow lines.
(a) Liganding residues in the 2-Ca
2+
form; (b) hydrogen bonding patterns within the 2-Ca
2+
form; (c) a similar view
of site II in the apo 0-Ca
2+
form of N-TnC.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1997,
273,
238-255)
copyright 1997.
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