PDBsum entry 1jc2

Structural protein

PDB id: 1jc2

Contents

Protein chain

75 a.a. *

Metals

_CA ×2

* Residue conservation analysis

PDB id:

1jc2

Name:

Structural protein

Title:

Complex of thE C-domain of troponin c with residues 1-40 of troponin i

Structure:

Troponin c, skeletal muscle. Chain: a. Fragment: residues 89-163 of gb entry 212778. Engineered: yes

Source:

Gallus gallus. Chicken. Organism_taxid: 9031. Gene: stnc. Expressed in: escherichia coli. Expression_system_taxid: 562.

NMR struc:

30 models

Authors:

P.Mercier,L.Spyracopoulos,B.D.Sykes

Key ref:

P.Mercier et al. (2001). Structure, dynamics, and thermodynamics of the structural domain of troponin C in complex with the regulatory peptide 1-40 of troponin I. Biochemistry, 40, 10063-10077. PubMed id: 11513585 DOI: 10.1021/bi010748+

Date:

07-Jun-01 Release date: 14-Sep-01

Protein chain

P02588  (TNNC2_CHICK) -  Troponin C, skeletal muscle from Gallus gallus

Seq: 163 a.a.

Struc: 75 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1021/bi010748+

Biochemistry 40:10063-10077 (2001)

PubMed id: 11513585

Structure, dynamics, and thermodynamics of the structural domain of troponin C in complex with the regulatory peptide 1-40 of troponin I.

P.Mercier, L.Spyracopoulos, B.D.Sykes.

ABSTRACT

The structure of the calcium-saturated C-domain of skeletal troponin C (CTnC) in complex with a regulatory peptide comprising residues 1-40 (Rp40) of troponin I (TnI) was determined using nuclear magnetic resonance (NMR) spectroscopy. The solution structure determined by NMR is similar to the structure of the C-domain from intact TnC in complex with TnI(1)(-)(47) determined by X-ray crystallography [Vassylyev, D. G., Takeda, S., Wakatsuki, S., Maeda, K., and Maeda, Y. (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 4847-4852]. Changes in the dynamic properties of CTnC.2Ca2+ induced by Rp40 binding were investigated using backbone amide (15)N NMR relaxation measurements. Analysis of NMR relaxation data allows for extraction of motional order parameters on a per residue basis, from which the contribution of changes in picosecond to nanosecond time scale motions to the conformational entropy associated with complex formation can be estimated. The results indicate that binding of Rp40 decreases backbone flexibility in CTnC, particularly at the end of the C-terminal helix. The backbone conformational entropy change (-TDeltaS) associated with binding of Rp40 to CTnC.2Ca2+ determined from (15)N relaxation data is 9.6 +/- 0.7 kcal mol(-1) at 30 degrees C. However, estimation of thermodynamic quantities using a structural approach [Lavigne, P., Bagu, J. R., Boyko, R., Willard, L., Holmes, C. F., and Sykes, B. D. (2000) Protein Sci. 9, 252-264] reveals that the change in solvation entropy upon complex formation is dominant and overcomes the thermodynamic "cost" associated with "stiffening" of the protein backbone upon Rp40 binding. Additionally, backbone amide (15)N relaxation data measured at different concentrations of CTnC.2Ca2+.Rp40 reveal that the complex dimerizes in solution. Fitting of the apparent global rotational correlation time as a function of concentration to a monomer-dimer equilibrium yields a dimerization constant of approximately 8.3 mM.