PDBsum entry 2b9c

Contractile protein

PDB id: 2b9c

Contents

Protein chains

136 a.a. *

Waters ×349

* Residue conservation analysis

PDB id:

2b9c

Name:

Contractile protein

Title:

Structure of tropomyosin's mid-region: bending and binding sites for actin

Structure:

Striated-muscle alpha tropomyosin. Chain: a, b. Engineered: yes

Source:

Rattus norvegicus. Norway rat. Organism_taxid: 10116. Expressed in: escherichia coli. Expression_system_taxid: 562

Biol. unit:

Dimer (from PQS)

Resolution:

2.30Å R-factor: 0.256 R-free: 0.296

Authors:

J.H.Brown,Z.Zhou,L.Reshetnikova,H.Robinson,R.D.Yammani,L.S.Tobacman, C.Cohen

Key ref:

J.H.Brown et al. (2005). Structure of the mid-region of tropomyosin: bending and binding sites for actin. Proc Natl Acad Sci U S A, 102, 18878-18883. PubMed id: 16365313 DOI: 10.1073/pnas.0509269102

Date:

11-Oct-05 Release date: 03-Jan-06

Protein chains

P04692  (TPM1_RAT) -  Tropomyosin alpha-1 chain from Rattus norvegicus

Seq: 284 a.a.

Struc: 136 a.a.*

* PDB and UniProt seqs differ at 20 residue positions (black crosses)

DOI no: 10.1073/pnas.0509269102

Proc Natl Acad Sci U S A 102:18878-18883 (2005)

PubMed id: 16365313

Structure of the mid-region of tropomyosin: bending and binding sites for actin.

J.H.Brown, Z.Zhou, L.Reshetnikova, H.Robinson, R.D.Yammani, L.S.Tobacman, C.Cohen.

ABSTRACT

Tropomyosin is a two-chain alpha-helical coiled coil whose periodic interactions with the F-actin helix are critical for thin filament stabilization and the regulation of muscle contraction. Here we deduce the mechanical and chemical basis of these interactions from the 2.3-A-resolution crystal structure of the middle three of tropomyosin's seven periods. Geometrically specific bends of the coiled coil, produced by clusters of core alanines, and variable bends about gaps in the core, produced by isolated alanines, occur along the molecule. The crystal packing is notable in signifying that the functionally important fifth period includes an especially favorable protein-binding site, comprising an unusual apolar patch on the surface together with surrounding charged residues. Based on these and other results, we have constructed a specific model of the thin filament, with the N-terminal halves of each period (i.e., the so-called "alpha zones") of tropomyosin axially aligned with subdomain 3 of each monomer in F-actin.

Selected figure(s)

Figure 2.
Fig. 2. Isolated core alanines create holes in the coiled coil. Shown is a series of space-filling models of consecutive stretches of the structure, each one viewing the broad face of the coiled coil. The region from residue 141 to the C terminus of the fragment is well packed [average gap volume = 30 Å3 per residue pair (see Table 4, which is published as supporting information on the PNAS web site)] whereas that from residues 113-141 contains significant holes in the core (average gap volume = 67 Å3 per residue pair). The quality of the packing between the helices of the coiled coil relates to the sequential pattern of the sizes of the side chains at the interface between the helices (see Results and letters in Fig. 3).

Figure 3.
Fig. 3. Specific bends from alanine staggers at low coiled-coil radii, and holes and variable bends from isolated core alanines at high radii. The graph shown is the coiled-coil radius at the location of each residue of MidTm. The letters on the graph are the one-letter code of the local core side chain; the printed size of the letter correlates with the mass of the side chain, and the color of the graph indicates whether the -helices have a local axial stagger greater than (blue) or less than (red) 1.0 Å. The cartoons depict different bends in the coiled coil (see Results); -helices are depicted by straight or curved rectangles, and their coiling around one another is not shown for clarity. See also Fig. 6 and ref. 22.

Figures were selected by an automated process.