PDBsum entry 2tn4

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protein metals links
Contractile system protein PDB id
Protein chain
155 a.a. *
_CA ×7
Waters ×97
* Residue conservation analysis
PDB id:
Name: Contractile system protein
Title: Four calcium tnc
Structure: Troponin c. Chain: a. Synonym: tnc. Engineered: yes. Mutation: yes. Other_details: rabbit skeletal troponin c
Source: Oryctolagus cuniculus. Rabbit. Organism_taxid: 9986. Tissue: muscle. Expressed in: escherichia coli. Expression_system_taxid: 562
2.00Å     R-factor:   0.212     R-free:   0.265
Authors: M.L.Love,R.Dominguez,A.Houdusse,C.Cohen
Key ref:
A.Houdusse et al. (1997). Structures of four Ca2+-bound troponin C at 2.0 A resolution: further insights into the Ca2+-switch in the calmodulin superfamily. Structure, 5, 1695-1711. PubMed id: 9438870 DOI: 10.1016/S0969-2126(97)00315-8
18-Sep-97     Release date:   08-Apr-98    
Go to PROCHECK summary

Protein chain
Pfam   ArchSchema ?
P02586  (TNNC2_RABIT) -  Troponin C, skeletal muscle
160 a.a.
155 a.a.*
Key:    PfamA domain  Secondary structure  CATH domain
* PDB and UniProt seqs differ at 1 residue position (black cross)

 Gene Ontology (GO) functional annotation 
  GO annot!
  Biochemical function     troponin T binding     3 terms  


DOI no: 10.1016/S0969-2126(97)00315-8 Structure 5:1695-1711 (1997)
PubMed id: 9438870  
Structures of four Ca2+-bound troponin C at 2.0 A resolution: further insights into the Ca2+-switch in the calmodulin superfamily.
A.Houdusse, M.L.Love, R.Dominguez, Z.Grabarek, C.Cohen.
BACKGROUND: In contrast to Ca2+4-bound calmodulin (CaM), which has evolved to bind to many target sequences and thus regulate the function of a variety of enzymes, troponin C (TnC) is a bistable switch which controls contraction in striated muscles. The specific target of TnC is troponin I (TnI), the inhibitory subunit of the troponin complex on the thin filaments of muscle. To date, only the crystal structure of Ca2+2-bound TnC (i.e. in the 'off' state) had been determined, which together with the structure of Ca2+4-bound CaM formed the basis for the so-called 'HMJ' model of the conformational changes in TnC upon Ca2+ binding. NMR spectroscopic studies of Ca2+4-bound TnC (i.e. in the 'on' state) have recently been carried out, but the detailed conformational changes that take place upon switching from the off to the on state have not yet been described. RESULTS: We have determined the crystal structures of two forms of expressed rabbit Ca2+4-bound TnC to 2.0 A resolution. The structures show that the conformation of the N-terminal lobe (N lobe) is similar to that predicted by the HMJ model. Our results also reveal, in detail, the residues involved in binding of Ca2+ in the regulatory N lobe of the molecule. We show that the central helix, which links the N and C lobes of TnC, is better stabilized in the Ca2+2-bound than in the Ca2+4-bound state of the molecule. Comparison of the crystal structures of the off and on states of TnC reveals the specific linkages in the molecule that change in the transition from off to on state upon Ca2+-binding. Small sequence differences are also shown to account for large functional differences between CaM and TnC. CONCLUSIONS: The two lobes of TnC are designed to respond to Ca2+-binding quite differently, although the structures with bound Ca2+ are very similar. A small number of differences in the sequences of these two lobes accounts for the fact that the C lobe is stabilized only in the open (Ca2+-bound) state, whereas the N lobe can switch between two stable states. This difference accounts for the Ca2+-dependent and Ca2+-independent interactions of the N and C lobe. The C lobe of TnC is always linked to TnI, whereas the N lobe can maintain its regulatory role - binding strongly to TnI at critical levels of Ca2+ - and in contrast, forming a stable closed conformation in the absence of Ca2+.
  Selected figure(s)  
Figure 6.
Figure 6. Conformational switch in the EF hands of the N lobe of TnC. Stereo diagram of the EF-hand domains I (a) and II (b) in the Ca^2+-free (yellow) and Ca^2+-bound (blue) structures of the N lobe of TnC. The helices of a domain are reoriented during the transition by conformational changes occurring in two hinge regions. The mechanism of the hinges is different, in EF-hands I and II, however. In particular, the hinge is more extended near helix B, rather than near helix D; this is because in EF-hand I, it involves not only residues from the b sheet but also residues T36-E38 (orange in the Ca^2+-free structure), which define an additional turn (cyan) of helix B when Ca^2+ is bound.
  The above figure is reprinted by permission from Cell Press: Structure (1997, 5, 1695-1711) copyright 1997.  
  Figure was selected by an automated process.  

Literature references that cite this PDB file's key reference

  PubMed id Reference
19920153 D.Kowlessur, and L.S.Tobacman (2010).
Troponin regulatory function and dynamics revealed by H/D exchange-mass spectrometry.
  J Biol Chem, 285, 2686-2694.  
19542563 I.M.Robertson, M.X.Li, and B.D.Sykes (2009).
Solution structure of human cardiac troponin C in complex with the green tea polyphenol, (-)-epigallocatechin 3-gallate.
  J Biol Chem, 284, 23012-23023.
PDB code: 2kdh
19184130 X.Xu, L.Zhang, D.Shen, H.Wu, L.Peng, and J.Li (2009).
Effect of metal ion substitutions in anticoagulation factor I from the venom of Agkistrodon acutus on the binding of activated coagulation factor X and on structural stability.
  J Biol Inorg Chem, 14, 559-571.  
17994617 M.M.Ribeiro, H.G.Franquelim, M.A.Castanho, and A.S.Veiga (2008).
Molecular interaction studies of peptides using steady-state fluorescence intensity. Static (de)quenching revisited.
  J Pept Sci, 14, 401-406.  
18162171 M.X.Li, I.M.Robertson, and B.D.Sykes (2008).
Interaction of cardiac troponin with cardiotonic drugs: a structural perspective.
  Biochem Biophys Res Commun, 369, 88-99.  
18329314 P.Trojan, N.Krauss, H.W.Choe, A.Giessl, A.Pulvermüller, and U.Wolfrum (2008).
Centrins in retinal photoreceptor cells: regulators in the connecting cilium.
  Prog Retin Eye Res, 27, 237-259.  
18231806 Y.M.Liou, S.C.Kuo, and S.R.Hsieh (2008).
Differential effects of a green tea-derived polyphenol (-)-epigallocatechin-3-gallate on the acidosis-induced decrease in the Ca(2+) sensitivity of cardiac and skeletal muscle.
  Pflugers Arch, 456, 787-800.  
16765896 E.Babini, I.Bertini, F.Capozzi, E.Chirivino, and C.Luchinat (2006).
A structural and dynamic characterization of the EF-hand protein CLSP.
  Structure, 14, 1029-1038.
PDB code: 2b1u
16475158 M.Nara, H.Morii, F.Yumoto, H.Kagi, and M.Tanokura (2006).
Fourier transform infrared spectroscopic study on the Ca2+ -bound coordination structures of synthetic peptide analogues of the calcium-binding site III of troponin C.
  Biopolymers, 82, 339-343.  
15576568 N.Uchikoga, S.Y.Takahashi, R.Ke, M.Sonoyama, and S.Mitaku (2005).
Electric charge balance mechanism of extended soluble proteins.
  Protein Sci, 14, 74-80.  
15709952 T.Kobayashi, and R.J.Solaro (2005).
Calcium, thin filaments, and the integrative biology of cardiac contractility.
  Annu Rev Physiol, 67, 39-67.  
15826946 T.M.Blumenschein, D.B.Stone, R.J.Fletterick, R.A.Mendelson, and B.D.Sykes (2005).
Calcium-dependent changes in the flexibility of the regulatory domain of troponin C in the troponin complex.
  J Biol Chem, 280, 21924-21932.  
15711886 M.X.Li, X.Wang, and B.D.Sykes (2004).
Structural based insights into the role of troponin in cardiac muscle pathophysiology.
  J Muscle Res Cell Motil, 25, 559-579.  
15205455 S.B.Tikunova, and J.P.Davis (2004).
Designing calcium-sensitizing mutations in the regulatory domain of cardiac troponin C.
  J Biol Chem, 279, 35341-35352.  
12886291 B.D.Sykes (2003).
Pulling the calcium trigger.
  Nat Struct Biol, 10, 588-589.  
12557238 B.Tripet, G.De Crescenzo, S.Grothe, M.O'Connor-McCourt, and R.S.Hodges (2003).
Kinetic analysis of the interactions between troponin C (TnC) and troponin I (TnI) binding peptides: evidence for separate binding sites for the 'structural' N-terminus and the 'regulatory' C-terminus of TnI on TnC.
  J Mol Recognit, 16, 37-53.  
12547787 C.Sheldahl, J.Xing, W.J.Dong, S.C.Harvey, and H.C.Cheung (2003).
The calcium-saturated cTnI/cTnC complex: structure of the inhibitory region of cTnI.
  Biophys J, 84, 1057-1064.  
12524267 F.Pitici (2003).
Structural preference for changes in the direction of the Ca2+-induced transition: a study of the regulatory domain of skeletal troponin-C.
  Biophys J, 84, 82.  
12840750 S.Takeda, A.Yamashita, K.Maeda, and Y.Maéda (2003).
Structure of the core domain of human cardiac troponin in the Ca(2+)-saturated form.
  Nature, 424, 35-41.
PDB codes: 1j1d 1j1e
12846843 Y.M.Liou, and M.W.Chen (2003).
Calcium-dependent protein-protein interactions induce changes in proximity relationships of Cys48 and Cys64 in chicken skeletal troponin I.
  Eur J Biochem, 270, 3092-3100.  
12147696 A.Dvoretsky, E.M.Abusamhadneh, J.W.Howarth, and P.R.Rosevear (2002).
Solution structure of calcium-saturated cardiac troponin C bound to cardiac troponin I.
  J Biol Chem, 277, 38565-38570.
PDB code: 1la0
12207022 D.G.Ward, M.P.Cornes, and I.P.Trayer (2002).
Structural consequences of cardiac troponin I phosphorylation.
  J Biol Chem, 277, 41795-41801.  
12022873 S.B.Tikunova, J.A.Rall, and J.P.Davis (2002).
Effect of hydrophobic residue substitutions with glutamine on Ca(2+) binding and exchange with the N-domain of troponin C.
  Biochemistry, 41, 6697-6705.  
12060657 X.Wang, M.X.Li, and B.D.Sykes (2002).
Structure of the regulatory N-domain of human cardiac troponin C in complex with human cardiac troponin I147-163 and bepridil.
  J Biol Chem, 277, 31124-31133.
PDB code: 1lxf
11341924 M.V.Medvedeva, D.R.Djemuchadze, D.M.Watterson, S.B.Marston, and N.B.Gusev (2001).
Replacement of Lys-75 of calmodulin affects its interaction with smooth muscle caldesmon.
  Biochim Biophys Acta, 1544, 143-150.  
11423417 Z.Li, J.Gergely, and T.Tao (2001).
Proximity relationships between residue 117 of rabbit skeletal troponin-I and residues in troponin-C and actin.
  Biophys J, 81, 321-333.  
  10933496 C.S.Tung, M.E.Wall, S.C.Gallagher, and J.Trewhella (2000).
A model of troponin-I in complex with troponin-C using hybrid experimental data: the inhibitory region is a beta-hairpin.
  Protein Sci, 9, 1312-1326.
PDB code: 1ew7
  10739260 I.Tsigelny, I.N.Shindyalov, P.E.Bourne, T.C.Südhof, and P.Taylor (2000).
Common EF-hand motifs in cholinesterases and neuroligins suggest a role for Ca2+ binding in cell surface associations.
  Protein Sci, 9, 180-185.  
11054120 K.Pääkkönen, T.Sorsa, T.Drakenberg, P.Pollesello, C.Tilgmann, P.Permi, S.Heikkinen, I.Kilpeläinen, and A.Annila (2000).
Conformations of the regulatory domain of cardiac troponin C examined by residual dipolar couplings.
  Eur J Biochem, 267, 6665-6672.  
10715110 P.Mercier, M.X.Li, and B.D.Sykes (2000).
Role of the structural domain of troponin C in muscle regulation: NMR studies of Ca2+ binding and subsequent interactions with regions 1-40 and 96-115 of troponin I.
  Biochemistry, 39, 2902-2911.  
10625482 T.Kobayashi, M.Kobayashi, Z.Gryczynski, J.R.Lakowicz, and J.H.Collins (2000).
Inhibitory region of troponin I: Ca(2+)-dependent structural and environmental changes in the troponin-tropomyosin complex and in reconstituted thin filaments.
  Biochemistry, 39, 86-91.  
10792039 Y.Li, M.L.Love, J.A.Putkey, and C.Cohen (2000).
Bepridil opens the regulatory N-terminal lobe of cardiac troponin C.
  Proc Natl Acad Sci U S A, 97, 5140-5145.
PDB code: 1dtl
11112516 Y.Luo, J.Leszyk, B.Li, J.Gergely, and T.Tao (2000).
Proximity relationships between residue 6 of troponin I and residues in troponin C: further evidence for extended conformation of troponin C in the troponin complex.
  Biochemistry, 39, 15306-15315.  
10209279 A.Yu, L.Ballard, L.Smillie, J.Pearlstone, D.Foguel, J.Silva, A.Jonas, and J.Jonas (1999).
Effects of high pressure and temperature on the wild-type and F29W mutant forms of the N-domain of avian troponin C.
  Biochim Biophys Acta, 1431, 53-63.  
10651267 J.Soman, T.Tao, and G.N.Phillips (1999).
Conformational variation of calcium-bound troponin C.
  Proteins, 37, 510-511.
PDB code: 1tcf
9876151 L.Smith, N.J.Greenfield, and S.E.Hitchcock-DeGregori (1999).
Mutations in the N- and D-helices of the N-domain of troponin C affect the C-domain and regulatory function.
  Biophys J, 76, 400-408.  
10364176 M.C.Moncrieffe, S.Eaton, Z.Bajzer, C.Haydock, J.D.Potter, T.M.Laue, and F.G.Prendergast (1999).
Rotational and translational motion of troponin C.
  J Biol Chem, 274, 17464-17470.  
10387074 M.X.Li, L.Spyracopoulos, and B.D.Sykes (1999).
Binding of cardiac troponin-I147-163 induces a structural opening in human cardiac troponin-C.
  Biochemistry, 38, 8289-8298.
PDB code: 1mxl
10220335 R.T.McKay, B.P.Tripet, J.R.Pearlstone, L.B.Smillie, and B.D.Sykes (1999).
Defining the region of troponin-I that binds to troponin-C.
  Biochemistry, 38, 5478-5489.  
10231519 S.Tsuda, A.Miura, S.M.Gagné, L.Spyracopoulos, and B.D.Sykes (1999).
Low-temperature-induced structural changes in the Apo regulatory domain of skeletal muscle troponin C.
  Biochemistry, 38, 5693-5700.
PDB codes: 1skt 1zac
10220325 T.Kobayashi, X.Zhao, R.Wade, and J.H.Collins (1999).
Involvement of conserved, acidic residues in the N-terminal domain of troponin C in calcium-dependent regulation.
  Biochemistry, 38, 5386-5391.  
10082949 T.Kobayashi, X.Zhao, R.Wade, and J.H.Collins (1999).
Ca2+-dependent interaction of the inhibitory region of troponin I with acidic residues in the N-terminal domain of troponin C.
  Biochim Biophys Acta, 1430, 214-221.  
10350487 Y.Luo, J.Leszyk, Y.Qian, J.Gergely, and T.Tao (1999).
Residues 48 and 82 at the N-terminal hydrophobic pocket of rabbit skeletal muscle troponin-C photo-cross-link to Met121 of troponin-I.
  Biochemistry, 38, 6678-6688.  
9560191 D.G.Vassylyev, S.Takeda, S.Wakatsuki, K.Maeda, and Y.Maéda (1998).
Crystal structure of troponin C in complex with troponin I fragment at 2.3-A resolution.
  Proc Natl Acad Sci U S A, 95, 4847-4852.
PDB code: 1a2x
9753452 K.Levay, D.K.Satpaev, A.N.Pronin, J.L.Benovic, and V.Z.Slepak (1998).
Localization of the sites for Ca2+-binding proteins on G protein-coupled receptor kinases.
  Biochemistry, 37, 13650-13659.  
9922172 L.Spyracopoulos, S.M.Gagné, M.X.Li, and B.D.Sykes (1998).
Dynamics and thermodynamics of the regulatory domain of human cardiac troponin C in the apo- and calcium-saturated states.
  Biochemistry, 37, 18032-18044.  
9730814 R.T.McKay, J.R.Pearlstone, D.C.Corson, S.M.Gagné, L.B.Smillie, and B.D.Sykes (1998).
Structure and interaction site of the regulatory domain of troponin-C when complexed with the 96-148 region of troponin-I.
  Biochemistry, 37, 12419-12430.
PDB code: 1blq
The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time. Where a reference describes a PDB structure, the PDB code is shown on the right.