2XN6

Crystal structure of thyroxine-binding globulin complexed with thyroxine-fluoresein


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.29 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.207 
  • R-Value Observed: 0.209 

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Ligand Structure Quality Assessment 


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:  
    2RIV, 2RIW, 2XN3, 2XN5, 2XN6, 2XN7

  • 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 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 ...

    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:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
THYROXINE-BINDING GLOBULINA350Homo sapiensMutation(s): 12 
Gene Names: SERPINA7TBG
UniProt & NIH Common Fund Data Resources
Find proteins for P05543 (Homo sapiens)
Explore P05543 
Go to UniProtKB:  P05543
PHAROS:  P05543
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP05543
Protein Feature View
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  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
THYROXINE-BINDING GLOBULINB35Homo sapiensMutation(s): 0 
Gene Names: SERPINA7TBG
UniProt & NIH Common Fund Data Resources
Find proteins for P05543 (Homo sapiens)
Explore P05543 
Go to UniProtKB:  P05543
PHAROS:  P05543
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP05543
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
Ligands 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
T44
Query on T44

Download Ideal Coordinates CCD File 
Q [auth A]3,5,3',5'-TETRAIODO-L-THYRONINE
C15 H11 I4 N O4
XUIIKFGFIJCVMT-LBPRGKRZSA-N
 Ligand Interaction
F6Y
Query on F6Y

Download Ideal Coordinates CCD File 
P [auth A]3',6'-DIHYDROXY-3-OXO-3H-SPIRO[2-BENZOFURAN-1,9'-XANTHENE]-6-CARBOXYLIC ACID
C21 H12 O7
BZTDTCNHAFUJOG-UHFFFAOYSA-N
 Ligand Interaction
EDO
Query on EDO

Download Ideal Coordinates CCD File 
D [auth A],
E [auth A],
G [auth A],
H [auth A],
J [auth A],
D [auth A],
E [auth A],
G [auth A],
H [auth A],
J [auth A],
K [auth A],
R [auth B]
1,2-ETHANEDIOL
C2 H6 O2
LYCAIKOWRPUZTN-UHFFFAOYSA-N
 Ligand Interaction
CA
Query on CA

Download Ideal Coordinates CCD File 
C [auth A],
F [auth A],
I [auth A],
L [auth A],
M [auth A],
C [auth A],
F [auth A],
I [auth A],
L [auth A],
M [auth A],
N [auth A],
O [auth A]
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.29 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.207 
  • R-Value Observed: 0.209 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 172.69α = 90
b = 42.14β = 90
c = 56.1γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
MOSFLMdata reduction
SCALEPACKdata scaling
PHASERphasing

Structure Validation

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Ligand Structure Quality Assessment 



Entry History 

Deposition Data

Revision History  (Full details and data files)

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