PDBsum entry 2jnf

Metal binding protein

PDB id: 2jnf

Contents

Protein chain

158 a.a. *

* Residue conservation analysis

PDB id:

2jnf

Name:

Metal binding protein

Title:

Solution structure of fly 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,B.Bullard,A.Pastore

Key ref:

G.De Nicola et al. (2007). The structure of Lethocerus troponin C: insights into the mechanism of stretch activation in muscles. Structure, 15, 813-824. PubMed id: 17637342 DOI: 10.1016/j.str.2007.05.007

Date:

18-Jan-07 Release date: 07-Aug-07

Protein chain

Q868D4  (Q868D4_LETIN) -  Troponin C from Lethocerus indicus

Seq: 158 a.a.

Struc: 158 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/j.str.2007.05.007

Structure 15:813-824 (2007)

PubMed id: 17637342

The structure of Lethocerus troponin C: insights into the mechanism of stretch activation in muscles.

G.De Nicola, C.Burkart, F.Qiu, B.Agianian, S.Labeit, S.Martin, B.Bullard, A.Pastore.

ABSTRACT

To gain a molecular description of how muscles can be activated by mechanical stretch, we have solved the structure of the calcium-loaded F1 isoform of troponin C (TnC) from Lethocerus and characterized its interactions with troponin I (TnI). We show that the presence of only one calcium cation in the fourth EF hand motif is sufficient to induce an open conformation in the C-terminal lobe of F1 TnC, in contrast with what is observed in vertebrate muscle. This lobe interacts in a calcium-independent way both with the N terminus of TnI and, with lower affinity, with a region of TnI equivalent to the switch and inhibitory peptides of vertebrate muscles. Using both synthetic peptides and recombinant proteins, we show that the N lobe of F1 TnC is not engaged in interactions with TnI, excluding a regulatory role of this domain. These findings provide insights into mechanically stimulated muscle contraction.

Selected figure(s)

Figure 2.
Figure 2. Conformational Status of the Two Lobes of F1 TnC
(A) Structural comparison of the two lobes of F1 TnC with the PDB picks up as the highest hits the apo N lobe of skeletal TnC, which is in closed conformation (PDB code: 1skt; Tsuda et al., 1999) and the holo C lobe of cardiac TnC in complex with the corresponding N terminus of TnI (PDB code: 1ozs; Lindhout and Sykes, 2003).
(B) Comparison of the HSQC spectra of apo (blue) and holo (red) Lethocerus F1 TnC. The spectra were recorded at 25°C on a 600 MHz spectrometer. The shift upon Ca^2+ addition of the resonance of V144 is indicated.

Figure 6.
Figure 6. Modeling of the Complex
(A) Structural superposition of the four available structures of TnC complexes (PDB codes: 1a2x, 1j1d, 1ytz, and 1yv0) with the N terminus of TnI. The structures were superposed on the C lobe of TnC. The comparison shows that, despite the differences in the relative orientation of the N lobe, TnI interacts in the same groove and adopts the same relative orientation to the C lobe.
(B) Comparison of the network of interactions formed between the C lobe of TnC and TnI in the cardiac complex (Takeda et al., 2003) (left panel) and in a homology model built (right panel) using the cardiac structure (PDB code: 1j1d) as a template. The side chains of the key residues involved are displayed explicitly and labeled in red and green according to whether they correspond to TnI and TnC, respectively, for the cardiac structure. Similarly, they are colored in red and blue according to whether they correspond to Lethocerus TnH and TnC, respectively.

The above figures are reprinted by permission from Cell Press: Structure (2007, 15, 813-824) copyright 2007.

Figures were selected by an automated process.