1SBJ

NMR Structure of the Mg2+-loaded C Terminal Domain of Cardiac Troponin C Bound to the N Terminal Domain of Cardiac Troponin I


Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 20 
  • Conformers Submitted: 20 
  • Selection Criteria: structures with the lowest energy 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

Structure of the Mg2+-loaded C-lobe of cardiac troponin C bound to the N-domain of cardiac troponin I: comparison with the Ca2+-loaded structure.

Finley, N.L.Howarth, J.W.Rosevear, P.R.

(2004) Biochemistry 43: 11371-11379

  • DOI: 10.1021/bi049672i
  • Structures With Same Primary Citation

  • PubMed Abstract: 
  • Cardiac troponin C (cTnC) is the Ca(2+)-binding component of the troponin complex and, as such, is the Ca(2+)-dependent switch in muscle contraction. This protein consists of two globular lobes, each containing a pair of EF-hand metal-binding sites, ...

    Cardiac troponin C (cTnC) is the Ca(2+)-binding component of the troponin complex and, as such, is the Ca(2+)-dependent switch in muscle contraction. This protein consists of two globular lobes, each containing a pair of EF-hand metal-binding sites, connected by a linker. In the N lobe, Ca(2+)-binding site I is inactive and Ca(2+)-binding site II is primarily responsible for initiation of muscle contraction. The C lobe contains Ca(2+)/Mg(2+)-binding sites III and IV, which bind Mg(2+) with lower affinity and play a structural as well as a secondary role in modulating the Ca(2+) signal. To understand the structural consequences of Ca(2+)/Mg(2+) exchange in the C lobe, we have determined the NMR solution structure of the Mg(2+)-loaded C lobe, cTnC(81-161), in a complex with the N domain of cardiac troponin I, cTnI(33-80), and compared it with a refined Ca(2+)-loaded structure. The overall tertiary structure of the Mg(2+)-loaded C lobe is very similar to that of the refined Ca(2+)-loaded structure as evidenced by the root-mean-square deviation of 0.94 A for all backbone atoms. While metal-dependent conformational changes are minimal, substitution of Mg(2+) for Ca(2+) is characterized by condensation of the C-terminal portion of the metal-binding loops with monodentate Mg(2+) ligation by the conserved Glu at position 12 and partial closure of the cTnI hydrophobic binding cleft around site IV. Thus, conformational plasticity in the Ca(2+)/Mg(2+)-dependent binding loops may represent a mechanism to modulate C-lobe cTnC interactions with the N domain of cTnI.


    Organizational Affiliation

    Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, College of Medicine, 231 Albert Sabin Way, Medical Sciences Building, Cincinnati Ohio 45267-0524, USA.



Macromolecules

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Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Troponin C, slow skeletal and cardiac musclesA81Gallus gallusMutation(s): 0 
Gene Names: cTnCTNNC1
Find proteins for P09860 (Gallus gallus)
Explore P09860 
Go to UniProtKB:  P09860
Protein Feature View
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  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MG
Query on MG

Download CCD File 
A
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 20 
  • Conformers Submitted: 20 
  • Selection Criteria: structures with the lowest energy 
  • OLDERADO: 1SBJ Olderado

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2004-11-23
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance