Crystal Structure of Sea Bream Transthyretin in complex with Triiodothyronine at 1.90A Resolution

Experimental Data Snapshot

  • Resolution: 1.90 Å
  • R-Value Free: 0.211 
  • R-Value Work: 0.173 
  • R-Value Observed: 0.177 

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High resolution crystal structures of piscine transthyretin reveal different binding modes for triiodothyronine and thyroxine.

Eneqvist, T.Lundberg, E.Karlsson, A.Huang, S.Santos, C.R.Power, D.M.Sauer-Eriksson, A.E.

(2004) J Biol Chem 279: 26411-26416

  • DOI: https://doi.org/10.1074/jbc.M313553200
  • Primary Citation of Related Structures:  
    1SN0, 1SN2, 1SN5

  • PubMed Abstract: 

    Transthyretin (TTR) is an extracellular transport protein involved in the distribution of thyroid hormones and vitamin A. So far, TTR has only been found in vertebrates, of which piscine TTR displays the lowest sequence identity with human TTR (47%). Human and piscine TTR bind both thyroid hormones 3,5,3'-triiodo-l-thyronine (T(3)) and 3,5,3',5'-tetraiodo-l-thyronine (thyroxine, T(4)). Human TTR has higher affinity for T(4) than T(3), whereas the reverse holds for piscine TTR. X-ray structures of Sparus aurata (sea bream) TTR have been determined as the apo-protein at 1.75 A resolution and bound to ligands T(3) and T(4), both at 1.9 A resolution. The apo structure is similar to human TTR with structural changes only at beta-strand D. This strand forms an extended loop conformation similar to the one in chicken TTR. The piscine TTR.T(4) complex shows the T(4)-binding site to be similar but not identical to human TTR, whereas the TTR.T(3) complex shows the I3' halogen situated at the site normally occupied by the hydroxyl group of T(4). The significantly wider entrance of the hormone-binding channel in sea bream TTR, in combination with its narrower cavity, provides a structural explanation for the different binding affinities of human and piscine TTR to T(3) and T(4).

  • Organizational Affiliation

    Umea Centre for Molecular Pathogenesis, Umea University, SE-901 87 Umea, Sweden.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C, D
130Sparus aurataMutation(s): 0 
Find proteins for Q9PTT3 (Sparus aurata)
Explore Q9PTT3 
Go to UniProtKB:  Q9PTT3
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9PTT3
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.90 Å
  • R-Value Free: 0.211 
  • R-Value Work: 0.173 
  • R-Value Observed: 0.177 
  • Space Group: P 41
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 58.284α = 90
b = 58.284β = 90
c = 138.904γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-08-03
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Refinement description, Version format compliance
  • Version 1.3: 2014-04-30
    Changes: Data collection
  • Version 2.0: 2023-11-15
    Changes: Atomic model, Data collection, Database references, Derived calculations