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PDBsum entry 1fi5
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Contractile protein
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PDB id
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1fi5
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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 structures of the c-Terminal domain of cardiac troponin c free and bound to the n-Terminal domain of cardiac troponin i.
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Authors
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G.M.Gasmi-Seabrook,
J.W.Howarth,
N.Finley,
E.Abusamhadneh,
V.Gaponenko,
R.M.Brito,
R.J.Solaro,
P.R.Rosevear.
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Ref.
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Biochemistry, 1999,
38,
8313-8322.
[DOI no: ]
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PubMed id
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Abstract
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The N-terminal domain of cardiac troponin I (cTnI) comprising residues 33-80 and
lacking the cardiac-specific amino terminus forms a stable binary complex with
the C-terminal domain of cardiac troponin C (cTnC) comprising residues 81-161.
We have utilized heteronuclear multidimensional NMR to assign the backbone and
side-chain resonances of Ca2+-saturated cTnC(81-161) both free and bound to
cTnI(33-80). No significant differences were observed between secondary
structural elements determined for free and cTnI(33-80)-bound cTnC(81-161). We
have determined solution structures of Ca2+-saturated cTnC(81-161) free and
bound to cTnI(33-80). While the tertiary structure of cTnC(81-161) is
qualitatively similar to that observed free in solution, the binding of
cTnI(33-80) results mainly in an opening of the structure and movement of the
loop region between helices F and G. Together, these movements provide the
binding site for the N-terminal domain of cTnI. The putative binding site for
cTnI(33-80) was determined by mapping amide proton and nitrogen chemical shift
changes, induced by the binding of cTnI(33-80), onto the C-terminal cTnC
structure. The binding interface for cTnI(33-80), as suggested from chemical
shift changes, involves predominantly hydrophobic interactions located in the
expanded hydrophobic pocket. The largest chemical shift changes were observed in
the loop region connecting helices F and G. Inspection of available TnC
sequences reveals that these residues are highly conserved, suggesting a common
binding motif for the Ca2+/Mg2+-dependent interaction site in the TnC/TnI
complex.
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