2CEO

thyroxine-binding globulin complex with thyroxine


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.8 Å
  • R-Value Free: 0.283 
  • R-Value Work: 0.235 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Structural Mechanism for the Carriage and Release of Thyroxine in the Blood.

Zhou, A.Wei, Z.Read, R.J.Carrell, R.W.

(2006) Proc.Natl.Acad.Sci.USA 103: 13321

  • DOI: 10.1073/pnas.0604080103

  • PubMed Abstract: 
  • The hormones that most directly control tissue activities in health and disease are delivered by two noninhibitory members of the serpin family of protease inhibitors, thyroxine-binding globulin (TBG) and corticosteroid-binding globulin. The structur ...

    The hormones that most directly control tissue activities in health and disease are delivered by two noninhibitory members of the serpin family of protease inhibitors, thyroxine-binding globulin (TBG) and corticosteroid-binding globulin. The structure of TBG bound to tetra-iodo thyroxine, solved here at 2.8 A, shows how the thyroxine is carried in a surface pocket on the molecule. This unexpected binding site is confirmed by mutations associated with a loss of hormone binding in both TBG and also homologously in corticosteroid-binding globulin. TBG strikingly differs from other serpins in having the upper half of its main beta-sheet fully opened, so its reactive center peptide loop can readily move in and out of the sheet to give an equilibrated binding and release of thyroxine. The entry of the loop triggers a conformational change, with a linked contraction of the binding pocket and release of the bound thyroxine. The ready reversibility of this change is due to the unique presence in the reactive loop of TBG of a proline that impedes the full and irreversible entry of the loop that occurs in other serpins. Thus, TBG has adapted the serpin inhibitory mechanism to give a reversible flip-flop transition, from a high-affinity to a low-affinity form. The complexity and ready triggering of this conformational mechanism strongly indicates that TBG has evolved to allow a modulated and targeted delivery of thyroxine to the tissues.


    Organizational Affiliation

    Departments of Haematology and Medicine, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 2XY, United Kingdom.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
THYROXINE-BINDING GLOBULIN
A, B
379Homo sapiensGene Names: SERPINA7 (TBG)
Find proteins for P05543 (Homo sapiens)
Go to Gene View: SERPINA7
Go to UniProtKB:  P05543
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
GOL
Query on GOL

Download SDF File 
Download CCD File 
A, B
GLYCEROL
GLYCERIN; PROPANE-1,2,3-TRIOL
C3 H8 O3
PEDCQBHIVMGVHV-UHFFFAOYSA-N
 Ligand Interaction
T44
Query on T44

Download SDF File 
Download CCD File 
A, B
3,5,3',5'-TETRAIODO-L-THYRONINE
C15 H11 I4 N O4
XUIIKFGFIJCVMT-LBPRGKRZSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
T44Kd: 0.1 nM PDBBIND
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.8 Å
  • R-Value Free: 0.283 
  • R-Value Work: 0.235 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 73.404α = 90.00
b = 88.022β = 90.00
c = 124.118γ = 90.00
Software Package:
Software NamePurpose
PHASERphasing
MOSFLMdata reduction
SCALAdata scaling
REFMACrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2006-08-14
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Advisory, Version format compliance