Crystal structure of human Transthyretin (TTR) at pH3.5

Experimental Data Snapshot

  • Resolution: 1.70 Å
  • R-Value Free: 0.260 
  • R-Value Work: 0.223 
  • R-Value Observed: 0.225 

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Structural insight into pH-induced conformational changes within the native human transthyretin tetramer.

Palaninathan, S.K.Mohamedmohaideen, N.N.Snee, W.C.Kelly, J.W.Sacchettini, J.C.

(2008) J Mol Biol 382: 1157-1167

  • DOI: https://doi.org/10.1016/j.jmb.2008.07.029
  • Primary Citation of Related Structures:  
    3CBR, 3D7P

  • PubMed Abstract: 

    Acidification of the transthyretin (TTR) tetramer facilitates dissociation and conformational changes in the protein, allowing alternatively folded monomers to self-assemble into insoluble amyloid fibers by a downhill polymerization mechanism in vitro. To investigate the influence of acidification on the quaternary and tertiary structures of TTR, crystal structures of wild-type human TTR at pH 4.0 and pH 3.5 have been determined to 1.7 A resolution. The acidic pH crystals are isomorphous to most of the previously reported TTR structures, containing two subunits in the asymmetric unit (the so-called A and B subunits) but forming a tetramer through crystallographic symmetry. The pH 4.0 crystal structure reveals that the native fold of the tetramer remains mostly undisturbed. In particular, subunit A of the TTR pH 4.0 structure is very similar to the wild-type TTR pH 7.4 structure with an r.m.s.d. of 0.38 A. In contrast, subunit B of the TTR pH 4.0 structure exhibits several significant changes. The EF-helix (residues 75-81) and the adjacent EF-loop (residues 82-90) show an r.m.s.d. greater than 2.0 A. The acidic residues within this region (Glu72, Asp74, Glu89, and Glu92) undergo significant conformational changes that instigate movement of the EF helix-loop region and make residues Lys70, Lys76, His88, and His90 orient their side chains toward these acidic residues. In particular, Glu89 undergoes a maximum deviation of 5.6 A, occupying Phe87's initial position in the wild-type TTR pH 7.4 structure, and points its side chain into a hydrophobic pocket of the neighboring subunit. In the pH 3.5 structure, the EF helix-loop region is completely disordered. These results demonstrate that acidic conditions increase the susceptibility of the EF helix-loop region of the TTR B subunit to undergo conformational changes and unfold, likely destabilizing the tetramer and identifying at least the initial conformational changes likely occurring within the tetramer that leads to the amyloidogenic monomer.

  • Organizational Affiliation

    Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
127Homo sapiensMutation(s): 0 
Gene Names: TTRPALB
UniProt & NIH Common Fund Data Resources
Find proteins for P02766 (Homo sapiens)
Explore P02766 
Go to UniProtKB:  P02766
PHAROS:  P02766
GTEx:  ENSG00000118271 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP02766
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.70 Å
  • R-Value Free: 0.260 
  • R-Value Work: 0.223 
  • R-Value Observed: 0.225 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 43.124α = 90
b = 85.494β = 90
c = 62.419γ = 90
Software Package:
Software NamePurpose
ADSCdata collection
HKL-2000data reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2008-08-12
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2023-08-30
    Changes: Data collection, Database references, Refinement description