3T3M

A Novel High Affinity Integrin alphaIIbbeta3 Receptor Antagonist That Unexpectedly Displaces Mg2+ from the beta3 MIDAS


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.60 Å
  • R-Value Free: 0.222 
  • R-Value Work: 0.179 
  • R-Value Observed: 0.180 

wwPDB Validation   3D Report Full Report



Literature

Structure-Guided Design of a High-Affinity Platelet Integrin alphaIIbbeta3 Receptor Antagonist That Disrupts Mg2+ Binding to the MIDAS

Zhu, J.Choi, W.S.McCoy, J.G.Negri, A.Zhu, J.Naini, S.Li, J.Shen, M.Huang, W.Bougie, D.Rasmussen, M.Aster, R.Thomas, C.J.Filizola, M.Springer, T.A.Coller, B.S.

(2012) Sci Transl Med 4: 125ra32-125ra32

  • DOI: 10.1126/scitranslmed.3003576
  • Primary Citation of Related Structures:  
    3T3M, 3T3P

  • PubMed Abstract: 
  • An integrin found on platelets, α(IIb)β(3) mediates platelet aggregation, and α(IIb)β(3) antagonists are effective antithrombotic agents in the clinic. Ligands bind to integrins in part by coordinating a magnesium ion (Mg(2+)) located in the β subunit me ...

    An integrin found on platelets, α(IIb)β(3) mediates platelet aggregation, and α(IIb)β(3) antagonists are effective antithrombotic agents in the clinic. Ligands bind to integrins in part by coordinating a magnesium ion (Mg(2+)) located in the β subunit metal ion-dependent adhesion site (MIDAS). Drugs patterned on the integrin ligand sequence Arg-Gly-Asp have a basic moiety that binds the α(IIb) subunit and a carboxyl group that coordinates the MIDAS Mg(2+) in the β(3) subunits. They induce conformational changes in the β(3) subunit that may have negative consequences such as exposing previously hidden epitopes and inducing the active conformation of the receptor. We recently reported an inhibitor of α(IIb)β(3) (RUC-1) that binds exclusively to the α(IIb) subunit; here, we report the structure-based design and synthesis of RUC-2, a RUC-1 derivative with a ~100-fold higher affinity. RUC-2 does not induce major conformational changes in β(3) as judged by monoclonal antibody binding, light scattering, gel chromatography, electron microscopy, and a receptor priming assay. X-ray crystallography of the RUC-2-α(IIb)β(3) headpiece complex in 1 mM calcium ion (Ca(2+))/5 mM Mg(2+) at 2.6 Å revealed that RUC-2 binds to α(IIb) the way RUC-1 does, but in addition, it binds to the β(3) MIDAS residue glutamic acid 220, thus displacing Mg(2+) from the MIDAS. When the Mg(2+) concentration was increased to 20 mM, however, Mg(2+) was identified in the MIDAS and RUC-2 was absent. RUC-2's ability to inhibit ligand binding and platelet aggregation was diminished by increasing the Mg(2+) concentration. Thus, RUC-2 inhibits ligand binding by a mechanism different from that of all other α(IIb)β(3) antagonists and may offer advantages as a therapeutic agent.


    Organizational Affiliation

    Immune Disease Institute, Children's Hospital Boston, and Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.



Macromolecules
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Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Integrin alpha-IIb AC457Homo sapiensMutation(s): 0 
Gene Names: ITGA2BGP2BITGAB
Find proteins for P08514 (Homo sapiens)
Explore P08514 
Go to UniProtKB:  P08514
NIH Common Fund Data Resources
PHAROS:  P08514
Protein Feature View
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  • Reference Sequence
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Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Integrin beta-3 BD472Homo sapiensMutation(s): 0 
Gene Names: ITGB3GP3A
Find proteins for P05106 (Homo sapiens)
Explore P05106 
Go to UniProtKB:  P05106
NIH Common Fund Data Resources
PHAROS:  P05106
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  • Reference Sequence
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Entity ID: 3
MoleculeChainsSequence LengthOrganismDetailsImage
Monoclonal antibody 10E5 heavy chain EH221Mus musculusMutation(s): 0 
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  • Reference Sequence
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Entity ID: 4
MoleculeChainsSequence LengthOrganismDetailsImage
Monoclonal antibody 10E5 light chain FL214Mus musculusMutation(s): 0 
Protein Feature View
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  • Reference Sequence
Oligosaccharides

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Entity ID: 5
MoleculeChainsChain Length2D Diagram Glycosylation3D Interactions
alpha-D-mannopyranose-(1-3)-[alpha-D-mannopyranose-(1-6)]beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
G
5 N-Glycosylation Oligosaccharides Interaction
Entity ID: 6
MoleculeChainsChain Length2D Diagram Glycosylation3D Interactions
2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
I, K
2 N-Glycosylation Oligosaccharides Interaction
Entity ID: 7
MoleculeChainsChain Length2D Diagram Glycosylation3D Interactions
alpha-D-mannopyranose-(1-3)-beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
J
4 N-Glycosylation Oligosaccharides Interaction
Small Molecules
Ligands 5 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
RC2
Query on RC2

Download Ideal Coordinates CCD File 
A, C
N-{3-[5-oxo-7-(piperazin-1-yl)-5H-[1,3,4]thiadiazolo[3,2-a]pyrimidin-2-yl]phenyl}glycinamide
C17 H19 N7 O2 S
ITNCYPYTFKVCFI-UHFFFAOYSA-N
 Ligand Interaction
NAG
Query on NAG

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B, D
2-acetamido-2-deoxy-beta-D-glucopyranose
C8 H15 N O6
OVRNDRQMDRJTHS-FMDGEEDCSA-N
 Ligand Interaction
SO4
Query on SO4

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A, L
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
CA
Query on CA

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A, B, C, D
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
CL
Query on CL

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B, C, D
CHLORIDE ION
Cl
VEXZGXHMUGYJMC-UHFFFAOYSA-M
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
RC2IC50:  95   nM  BindingDB
RC2IC50:  96   nM  BindingDB
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.60 Å
  • R-Value Free: 0.222 
  • R-Value Work: 0.179 
  • R-Value Observed: 0.180 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 261.15α = 90
b = 145.33β = 90
c = 104.68γ = 90
Software Package:
Software NamePurpose
Blu-Icedata collection
PHASERphasing
PHENIXrefinement
XDSdata reduction
XDSdata scaling

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2012-03-28
    Type: Initial release
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Advisory, Atomic model, Data collection, Derived calculations, Structure summary