2XN3

Crystal structure of thyroxine-binding globulin complexed with mefenamic acid


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.09 Å
  • R-Value Free: 0.260 
  • R-Value Work: 0.210 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Allosteric Modulation of Hormone Release from Thyroxine and Corticosteroid Binding-Globulins.

Qi, X.Loiseau, F.Chan, W.L.Yan, Y.Wei, Z.Milroy, L.G.Myers, R.M.Ley, S.V.Read, R.J.Carrell, R.W.Zhou, A.

(2011) J.Biol.Chem. 286: 16163

  • DOI: 10.1074/jbc.M110.171082
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • The release of hormones from thyroxine-binding globulin (TBG) and corticosteroid-binding globulin (CBG) is regulated by movement of the reactive center loop in and out of the β-sheet A of the molecule. To investigate how these changes are transmitted ...

    The release of hormones from thyroxine-binding globulin (TBG) and corticosteroid-binding globulin (CBG) is regulated by movement of the reactive center loop in and out of the β-sheet A of the molecule. To investigate how these changes are transmitted to the hormone-binding site, we developed a sensitive assay using a synthesized thyroxine fluorophore and solved the crystal structures of reactive loop cleaved TBG together with its complexes with thyroxine, the thyroxine fluorophores, furosemide, and mefenamic acid. Cleavage of the reactive loop results in its complete insertion into the β-sheet A and a substantial but incomplete decrease in binding affinity in both TBG and CBG. We show here that the direct interaction between residue Thr(342) of the reactive loop and Tyr(241) of the hormone binding site contributes to thyroxine binding and release following reactive loop insertion. However, a much larger effect occurs allosterically due to stretching of the connecting loop to the top of the D helix (hD), as confirmed in TBG with shortening of the loop by three residues, making it insensitive to the S-to-R transition. The transmission of the changes in the hD loop to the binding pocket is seen to involve coherent movements in the s2/3B loop linked to the hD loop by Lys(243), which is, in turn, linked to the s4/5B loop, flanking the thyroxine-binding site, by Arg(378). Overall, the coordinated movements of the reactive loop, hD, and the hormone binding site allow the allosteric regulation of hormone release, as with the modulation demonstrated here in response to changes in temperature.


    Organizational Affiliation

    Department of Biochemistry, Nanjing University, Nanjing, China.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
THYROXINE-BINDING GLOBULIN
A
343Homo sapiensMutation(s): 9 
Gene Names: SERPINA7 (TBG)
Find proteins for P05543 (Homo sapiens)
Go to Gene View: SERPINA7
Go to UniProtKB:  P05543
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
THYROXINE-BINDING GLOBULIN
B
40Homo sapiensMutation(s): 0 
Gene Names: SERPINA7 (TBG)
Find proteins for P05543 (Homo sapiens)
Go to Gene View: SERPINA7
Go to UniProtKB:  P05543
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
ID8
Query on ID8

Download SDF File 
Download CCD File 
A
2-[(2,3-DIMETHYLPHENYL)AMINO]BENZOIC ACID
MEFENAMIC ACID
C15 H15 N O2
HYYBABOKPJLUIN-UHFFFAOYSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
ID8Kd: 89 nM BINDINGMOAD
ID8Kd: 1198 nM PDBBIND
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.09 Å
  • R-Value Free: 0.260 
  • R-Value Work: 0.210 
  • Space Group: P 21 21 2
Unit Cell:
Length (Å)Angle (°)
a = 172.835α = 90.00
b = 41.624β = 90.00
c = 56.188γ = 90.00
Software Package:
Software NamePurpose
REFMACrefinement
PHASERphasing
MOSFLMdata reduction
SCALEPACKdata scaling

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2011-02-16
    Type: Initial release
  • Version 1.1: 2011-05-08
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance