PDBsum entry 2k2a

Go to PDB code: 
protein links
Contractile protein PDB id
Protein chain
70 a.a. *
* Residue conservation analysis
PDB id:
Name: Contractile protein
Title: Solution structure of the apo c terminal domain of lethoceru c isoform f1
Structure: Troponin c. Chain: a. Engineered: yes
Source: Lethocerus indicus. Organism_taxid: 212017. Gene: tnc4. Expressed in: escherichia coli. Expression_system_taxid: 562.
NMR struc: 10 models
Authors: G.F.De Nicola,G.Kelly,B.Bullard,J.Mccormick
Key ref: G.F.De Nicola et al. (2010). Solution structure of the Apo C-terminal domain of the Lethocerus F1 troponin C isoform. Biochemistry, 49, 1719-1726. PubMed id: 20104876
29-Mar-08     Release date:   07-Apr-09    
Go to PROCHECK summary

Protein chain
Pfam   ArchSchema ?
Q868D4  (Q868D4_9HEMI) -  Troponin C
158 a.a.
70 a.a.
Key:    PfamA domain  Secondary structure

 Gene Ontology (GO) functional annotation 
  GO annot!
  Biochemical function     calcium ion binding     1 term  


Biochemistry 49:1719-1726 (2010)
PubMed id: 20104876  
Solution structure of the Apo C-terminal domain of the Lethocerus F1 troponin C isoform.
G.F.De Nicola, S.Martin, B.Bullard, A.Pastore.
Muscle contraction is activated by two distinct mechanisms. One depends on the calcium influx, and the other is calcium-independent and activated by mechanical stress. A prototypical example of stretch activation is observed in insect muscles. In Lethocerus, a model system ideally suited for studying stretch activation, the two mechanisms seem to be under the control of different isoforms of troponin C (TnC), F1 and F2, which are responsible for stretch and calcium-dependent regulation, respectively. We have previously shown that F1 TnC is a typical collapsed dumbbell EF-hand protein that accommodates one calcium ion in its fourth EF-hand. When calcium loaded, the C-terminal domain of F1 TnC is in an open conformation which allows binding to troponin I. We have determined the solution structure of the isolated F1 TnC C-terminal domain in the absence of calcium and have compared it together with its dynamical properties with those of the calcium-loaded form. The domain is folded also in the absence of calcium and is in a closed conformation. Binding of a single calcium is sufficient to induce a modest but clear closed-to-open conformational transition and releases the conformational entropy observed in the calcium-free form. These results provide the first example of a TnC domain in which the presence of only one calcium ion is sufficient to induce a closed-to-open transition and clarify the role of calcium in stretch activation.