PDBsum entry 2avg

Structural protein

PDB id: 2avg

Contents

Protein chain

110 a.a. *

* Residue conservation analysis

PDB id:

2avg

Name:

Structural protein

Title:

Nmr structure of cc1 domain from human cardiac myosin binding protein c

Structure:

Myosin-binding protein c, cardiac-type. Chain: a. Fragment: cc1 domain. Synonym: cardiac mybp-c, c-protein, cardiac muscle isoform. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli. Expression_system_taxid: 562.

NMR struc:

29 models

Authors:

A.Ababou,M.Gautel,M.Pfuhl

Key ref:

A.Ababou et al. (2008). Myosin binding protein C positioned to play a key role in regulation of muscle contraction: structure and interactions of domain C1. J Mol Biol, 384, 615-630. PubMed id: 18926831 DOI: 10.1016/j.jmb.2008.09.065

Date:

30-Aug-05 Release date: 05-Sep-06

Protein chain

Q14896  (MYPC3_HUMAN) -  Myosin-binding protein C, cardiac-type from Homo sapiens

Seq: 1274 a.a.

Struc: 110 a.a.*

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

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/j.jmb.2008.09.065

J Mol Biol 384:615-630 (2008)

PubMed id: 18926831

Myosin binding protein C positioned to play a key role in regulation of muscle contraction: structure and interactions of domain C1.

A.Ababou, E.Rostkova, S.Mistry, C.Le Masurier, M.Gautel, M.Pfuhl.

ABSTRACT

Myosin binding protein C (MyBP-C) is a thick filament protein involved in the regulation of muscle contraction. Mutations in the gene for MyBP-C are the second most frequent cause of hypertrophic cardiomyopathy. MyBP-C binds to myosin with two binding sites, one at its C-terminus and another at its N-terminus. The N-terminal binding site, consisting of immunoglobulin domains C1 and C2 connected by a flexible linker, interacts with the S2 segment of myosin in a phosphorylation-regulated manner. It is assumed that the function of MyBP-C is to act as a tether that fixes the S1 heads in a resting position and that phosphorylation releases the S1 heads into an active state. Here, we report the structure and binding properties of domain C1. Using a combination of site-directed mutagenesis and NMR interaction experiments, we identified the binding site of domain C1 in the immediate vicinity of the S1-S2 hinge, very close to the light chains. In addition, we identified a zinc binding site on domain C1 in close proximity to the S2 binding site. Its zinc binding affinity (K(d) of approximately 10-20 microM) might not be sufficient for a physiological effect. However, the familial hypertrophic cardiomyopathy-related mutation of one of the zinc ligands, glutamine 210 to histidine, will significantly increase the binding affinity, suggesting that this mutation may affect S2 binding. The close proximity of the C1 binding site to the hinge, the light chains and the S1 heads also provides an explanation for recent observations that (a) shorter fragments of MyBP-C unable to act as a tether still have an effect on the actomyosin ATPase and (b) as to why the myosin head positions in phosphorylated wild-type mice and MyBP-C knockout mice are so different: Domain C1 bound to the S1-S2 hinge is able to manipulate S1 head positions, thus influencing force generation without tether. The potentially extensive extra interactions of C1 are expected to keep it in place, while phosphorylation dislodges the C1-C2 linker and domain C2. As a result, the myosin heads would always be attached to a tether that has phosphorylation-dependent length regulation.

Selected figure(s)

Figure 3.
Fig. 3. Zinc binding of C1. (a) Detailed view of the zinc binding site in the structure of C1. Only side chains of Gln208, His210, Glu223 and His225 are shown. A zinc atom has been modelled in the binding site. After energy minimisation, the zinc-ligand distances are 2.27 Å for His210(Ne2), 2.26 Å for His225(Ne2), 1.60 Å for Glu223(Oe1), 1.81 Å for Glu223 (Oe2) and 2.22 Å for Gln208(Oe1). (b) Plot of chemical shift perturbation against the protein sequence. The first red line represents the angle bracket Δδ angle bracket [tot] level, and the second red line is angle bracket Δδ angle bracket [tot] + 1*σ. Residues with chemical shift perturbations above angle bracket Δδ angle bracket [tot] + 1*σ are explicitly labelled. (b) Titration curves for residues in fast exchange for estimating binding affinity and stoichiometry. (c) Mapping of chemical shift perturbations on the three-dimensional structure of C1. Residues with chemical shift perturbations above angle bracket Δδ angle bracket [tot] + 1*σ are shown as spheres. The residues expected to coordinate the zinc are shown in red (histidines) and blue (glutamate/glutamine), and those with significant perturbations not expected to be directly involved are shown in green. (d) Titration curves for residues in fast exchange for estimating binding affinity and stoichiometry.

Figure 7.
Fig. 7. Model of the complex of C1 and S2Δ. (a) Overview of the position of C1 (blue) on S2Δ (red). Amino acids in C1 with chemical shift perturbations larger than angle bracket Δδ angle bracket [tot] are marked by green spheres on their N positions. (b) Detailed view of the interactions of C1 and S2Δ in the model. C1 is shown in blue, and S2Δ is shown in red. Important side chains in the interaction are coloured by atom type (carbon, green; oxygen, red; nitrogen, blue), and labels are coloured by protein. (c) Depiction of the overall assembly of C1 and C2 and the linker on S2Δ. Domains C1 and C2 of MyBP-C are shown in orange, and the linker between them is shown in gray. The three phosphorylation sites in the linker are shown in purple, residues mutated in FHC are shown in yellow with labels and charged residues are coloured according to their charge. S2Δ is shown with solvent-accessible surface coloured by a simple electrostatic potential with the N-terminus on the left (hidden by C1) and the C-terminus on the right. The position of the C-terminal cluster of FHC-related point mutations in S2Δ is indicated by the residue numbers (924–936).

The above figures are reprinted from an Open Access publication published by Elsevier: J Mol Biol (2008, 384, 615-630) copyright 2008.

Figures were selected by the author.