Crystal structure of the FnIII-tandem A77-A78 from the A-band of titin

Experimental Data Snapshot

  • Resolution: 1.65 Å
  • R-Value Free: 0.208 
  • R-Value Work: 0.179 
  • R-Value Observed: 0.179 

wwPDB Validation   3D Report Full Report

This is version 1.2 of the entry. See complete history


The structure of the FnIII Tandem A77-A78 points to a periodically conserved architecture in the myosin-binding region of titin

Bucher, R.M.Svergun, D.I.Muhle-Goll, C.Mayans, O.

(2010) J Mol Biol 401: 843-853

  • DOI: https://doi.org/10.1016/j.jmb.2010.06.011
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Titin is a large intrasarcomeric protein that, among its many roles in muscle, is thought to modulate the in vivo assembly of the myosin motor filament. This is achieved through the molecular template properties of its A-band region, which is composed of fibronectin type III (FnIII) and immunoglobulin (Ig) domains organized into characteristic 7-domain (D-zone) and 11-domain (C-zone) superrepeats. Currently, there is little knowledge on the structural details of this region of titin. Here we report the conformational characterization of three FnIII tandems, A77-A78, A80-A82, and A84-A86, which are components of the representative fourth C-zone superrepeat. The structure of A77-A78 has been elucidated by X-ray crystallography to 1.65 A resolution, while low-resolution models of A80-A82 and A84-A86 have been calculated using small-angle X-ray scattering. A77-A78 adopts an extended "up-down" domain arrangement, where domains are connected by a hydrophilic three-residue linker sequence. The linker is embedded in a rich network of polar contacts at the domain interface that results in a stiff molecular conformation. The models of A80-A82 and A84-A86, which contain hydrophobic six-residue-long interdomain linkers, equally showed elongated molecular shapes, but with slightly coiled or zigzagged conformations. Small-angle X-ray scattering data further suggested that the long linkers do not result in a noticeable increase in molecular flexibility but lead to semibent domain arrangements. Our findings indicate that the structural characteristics of FnIII tandems from A-band titin contrast markedly with those of poly-Ig tandems from the elastic I-band, which exhibit domain interfaces depleted of interactions and compliant conformations. Furthermore, the analysis of sequence conservation in FnIII domains from A-band titin points to the existence of conformationally defined interfaces at specific superrepeat positions, possibly leading to a periodic and locally ordered architecture supporting the molecular scaffold properties of this region of titin.

  • Organizational Affiliation

    Division of Structural Biology, Biozentrum, University of Basel, Klingelbergstr. 70, CH-4056 Basel, Switzerland.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A77-A78 domain from Titin
A, B
197Homo sapiensMutation(s): 0 
Gene Names: TTN
UniProt & NIH Common Fund Data Resources
Find proteins for Q8WZ42 (Homo sapiens)
Explore Q8WZ42 
Go to UniProtKB:  Q8WZ42
GTEx:  ENSG00000155657 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8WZ42
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.65 Å
  • R-Value Free: 0.208 
  • R-Value Work: 0.179 
  • R-Value Observed: 0.179 
  • Space Group: C 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 115.9α = 90
b = 163.2β = 90
c = 65.2γ = 90
Software Package:
Software NamePurpose
MAR345dtbdata collection
XDSdata reduction
XSCALEdata scaling

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2010-09-08
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2023-11-01
    Changes: Data collection, Database references, Derived calculations, Refinement description