1MXL

STRUCTURE OF CARDIAC TROPONIN C-TROPONIN I COMPLEX


Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 40 
  • Selection Criteria: LEAST RESTRAINT VIOLATION 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Binding of cardiac troponin-I147-163 induces a structural opening in human cardiac troponin-C.

Li, M.X.Spyracopoulos, L.Sykes, B.D.

(1999) Biochemistry 38: 8289-8298

  • DOI: 10.1021/bi9901679
  • Also Cited By: 2KFX

  • PubMed Abstract: 
  • The interaction of troponin-C (TnC) with troponin-I (TnI) plays a central role in skeletal and cardiac muscle contraction. We have recently shown that the binding of Ca2+ to cardiac TnC (cTnC) does not induce an "opening" of the regulatory domain in ...

    The interaction of troponin-C (TnC) with troponin-I (TnI) plays a central role in skeletal and cardiac muscle contraction. We have recently shown that the binding of Ca2+ to cardiac TnC (cTnC) does not induce an "opening" of the regulatory domain in order to interact with cTnI [Sia, S. K., et al. (1997) J. Biol. Chem. 272, 18216-18221; Spyracopoulos et al. (1997) Biochemistry 36, 12138-12146], which is in contrast to the regulatory N-domain of skeletal TnC (sTnC). This implies that the mode of interaction between cTnC and cTnI may be different than that between sTnC and sTnI. In sTnI, a region downstream from the inhibitory region (residues 115-131) has been shown to bind the exposed hydrophobic pocket of Ca2+-saturated sNTnC [McKay, R. T., et al. (1997) J. Biol. Chem. 272, 28494-28500]. The present study demonstrates that the corresponding region in cTnI (residues 147-163) binds to the regulatory domain of cTnC only in the Ca2+-saturated state to form a 1:1 complex, with an affinity approximately six times weaker than that between the skeletal counterparts. Thus, while Ca2+ does not cause opening, it is required for muscle regulation. The solution structure of the cNTnC.Ca2+.cTnI147-163 complex has been determined by multinuclear multidimensional NMR spectroscopy. The structure reveals an open conformation for cNTnC, similar to that of Ca2+-saturated sNTnC. The bound peptide adopts a alpha-helical conformation spanning residues 150-157. The C-terminus of the peptide is unstructured. The open conformation for Ca2+-saturated cNTnC in the presence of cTnI (residues 147-163) accommodates hydrophobic interactions between side chains of the peptide and side chains at the interface of A and B helices of cNTnC. Thus the mechanistic differences between the regulation of cardiac and skeletal muscle contraction can be understood in terms of different thermodynamics and kinetics equilibria between essentially the same structure states.


    Organizational Affiliation

    MRC Group in Protein Structure and Function, Department of Biochemistry, University of Alberta, Edmonton, Canada.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
PROTEIN (TROPONIN C)
C
89Homo sapiensGene Names: TNNC1 (TNNC)
Find proteins for P63316 (Homo sapiens)
Go to Gene View: TNNC1
Go to UniProtKB:  P63316
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
PROTEIN (TROPONIN I)
I
17Homo sapiensGene Names: TNNI3 (TNNC1)
Find proteins for P19429 (Homo sapiens)
Go to Gene View: TNNI3
Go to UniProtKB:  P19429
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CA
Query on CA

Download SDF File 
Download CCD File 
C
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 40 
  • Selection Criteria: LEAST RESTRAINT VIOLATION 
  • Olderado: 1MXL Olderado

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1999-07-06
    Type: Initial release
  • Version 1.1: 2008-04-26
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance