PDBsum entry 1ytz

Contractile protein

PDB id: 1ytz

Contents

Protein chains

90 a.a. *

141 a.a. *

159 a.a. *

Ligands

DR6 ×3

Metals

_CA ×4

Waters ×33

* Residue conservation analysis

PDB id:

1ytz

Name:

Contractile protein

Title:

Crystal structure of skeletal muscle troponin in the ca2+-activated state

Structure:

Troponin t. Chain: t. Engineered: yes. Troponin i. Chain: i. Synonym: troponin i, fast-twitch isoform. Engineered: yes. Troponin c. Chain: c.

Source:

Gallus gallus. Chicken. Organism_taxid: 9031. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008. Gene: tnnc2.

Biol. unit:

Hexamer (from PQS)

Resolution:

3.00Å R-factor: 0.289 R-free: 0.338

Authors:

M.V.Vinogradova,D.B.Stone,G.G.Malanina,C.Karatzaferi,R.Cooke, R.A.Mendelson,R.J.Fletterick

Key ref:

M.V.Vinogradova et al. (2005). Ca(2+)-regulated structural changes in troponin. Proc Natl Acad Sci U S A, 102, 5038-5043. PubMed id: 15784741 DOI: 10.1073/pnas.0408882102

Date:

11-Feb-05 Release date: 12-Apr-05

Protein chain

P12620  (TNNT3_CHICK) -  Troponin T, fast skeletal muscle isoforms from Gallus gallus

Seq: 263 a.a.

Struc: 90 a.a.

Protein chain

P68246  (TNNI2_CHICK) -  Troponin I, fast skeletal muscle from Gallus gallus

Seq: 183 a.a.

Struc: 141 a.a.*

Protein chain

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

Seq: 163 a.a.

Struc: 159 a.a.

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

DOI no: 10.1073/pnas.0408882102

Proc Natl Acad Sci U S A 102:5038-5043 (2005)

PubMed id: 15784741

Ca(2+)-regulated structural changes in troponin.

M.V.Vinogradova, D.B.Stone, G.G.Malanina, C.Karatzaferi, R.Cooke, R.A.Mendelson, R.J.Fletterick.

ABSTRACT

Troponin senses Ca2+ to regulate contraction in striated muscle. Structures of skeletal muscle troponin composed of TnC (the sensor), TnI (the regulator), and TnT (the link to the muscle thin filament) have been determined. The structure of troponin in the Ca(2+)-activated state features a nearly twofold symmetrical assembly of TnI and TnT subunits penetrated asymmetrically by the dumbbell-shaped TnC subunit. Ca ions are thought to regulate contraction by controlling the presentation to and withdrawal of the TnI inhibitory segment from the thin filament. Here, we show that the rigid central helix of the sensor binds the inhibitory segment of TnI in the Ca(2+)-activated state. Comparison of crystal structures of troponin in the Ca(2+)-activated state at 3.0 angstroms resolution and in the Ca(2+)-free state at 7.0 angstroms resolution shows that the long framework helices of TnI and TnT, presumed to be a Ca(2+)-independent structural domain of troponin are unchanged. Loss of Ca ions causes the rigid central helix of the sensor to collapse and to release the inhibitory segment of TnI. The inhibitory segment of TnI changes conformation from an extended loop in the presence of Ca2+ to a short alpha-helix in its absence. We also show that Anapoe, a detergent molecule, increases the contractile force of muscle fibers and binds specifically, together with the TnI switch helix, in a hydrophobic pocket of TnC upon activation by Ca ions.

Selected figure(s)

Figure 3.
Fig. 3. Superposition of the structures of chicken skeletal muscle troponin and human cardiac troponin in the Ca^2+-saturated state. The structure of cardiac troponin (28) (PDB ID code 1J1D [PDB] ; chains A, B, and C) is shown in gray. Arrows indicate deviations.

Figure 5.
Fig. 5. Cartoon representation of the conformational changes occurring in troponin during muscle contraction. For color coding, see the legend to Fig. 1. Ca ions are shown as black circles. The hydrophobic pocket opened in the N-terminal lobe of TnC is colored in green. The switch segment and the inhibitory segment of TnI are indicated.

Figures were selected by an automated process.