PDBsum entry 2k2a

Contractile protein

PDB id: 2k2a

Contents

Protein chain

70 a.a. *

* Residue conservation analysis

PDB id:

2k2a

Name:

Contractile protein

Title:

Solution structure of the apo c terminal domain of lethocerus troponin 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

Date:

29-Mar-08 Release date: 07-Apr-09

Protein chain

Q868D4  (Q868D4_LETIN) -  Troponin C from Lethocerus indicus

Seq: 158 a.a.

Struc: 70 a.a.

Enzyme reactions

• Enzyme class: E.C.?

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.

ABSTRACT

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.