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 

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Ligand Structure Quality Assessment 


This is version 2.0 of the entry. See complete history


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 metal ion-dependent adhesion site (MIDAS) ...

    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-IIbA, C457Homo sapiensMutation(s): 0 
Gene Names: ITGA2BGP2BITGAB
UniProt & NIH Common Fund Data Resources
Find proteins for P08514 (Homo sapiens)
Explore P08514 
Go to UniProtKB:  P08514
PHAROS:  P08514
GTEx:  ENSG00000005961 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP08514
Protein Feature View
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Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Integrin beta-3B, D472Homo sapiensMutation(s): 0 
Gene Names: ITGB3GP3A
UniProt & NIH Common Fund Data Resources
Find proteins for P05106 (Homo sapiens)
Explore P05106 
Go to UniProtKB:  P05106
PHAROS:  P05106
GTEx:  ENSG00000259207 
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UniProt GroupP05106
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Entity ID: 3
MoleculeChainsSequence LengthOrganismDetailsImage
Monoclonal antibody 10E5 heavy chainE,
G [auth H]
221Mus musculusMutation(s): 0 
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Entity ID: 4
MoleculeChainsSequence LengthOrganismDetailsImage
Monoclonal antibody 10E5 light chainF,
H [auth L]
214Mus musculusMutation(s): 0 
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  • Reference Sequence
Oligosaccharides

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Entity ID: 5
MoleculeChainsChain Length2D DiagramGlycosylation3D 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-glucopyranoseI [auth G]5N-Glycosylation Oligosaccharides Interaction
Glycosylation Resources
GlyTouCan:  G22768VO
GlyCosmos:  G22768VO
GlyGen:  G22768VO
Entity ID: 6
MoleculeChainsChain Length2D DiagramGlycosylation3D Interactions
2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranoseJ [auth I],
L [auth K]
2N-Glycosylation Oligosaccharides Interaction
Glycosylation Resources
GlyTouCan:  G42666HT
GlyCosmos:  G42666HT
GlyGen:  G42666HT
Entity ID: 7
MoleculeChainsChain Length2D DiagramGlycosylation3D 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-glucopyranoseK [auth J]4N-Glycosylation Oligosaccharides Interaction
Glycosylation Resources
GlyTouCan:  G81315DD
GlyCosmos:  G81315DD
GlyGen:  G81315DD
Small Molecules
Ligands 5 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
RC2
Query on RC2

Download Ideal Coordinates CCD File 
CA [auth C],
Q [auth A]
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

Download Ideal Coordinates CCD File 
GA [auth D],
W [auth B]
2-acetamido-2-deoxy-beta-D-glucopyranose
C8 H15 N O6
OVRNDRQMDRJTHS-FMDGEEDCSA-N
 Ligand Interaction
SO4
Query on SO4

Download Ideal Coordinates CCD File 
IA [auth L],
R [auth A],
S [auth A],
T [auth A]
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
CA
Query on CA

Download Ideal Coordinates CCD File 
AA [auth C],
BA [auth C],
EA [auth D],
FA [auth D],
M [auth A],
AA [auth C],
BA [auth C],
EA [auth D],
FA [auth D],
M [auth A],
N [auth A],
O [auth A],
P [auth A],
U [auth B],
V [auth B],
Y [auth C],
Z [auth C]
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
CL
Query on CL

Download Ideal Coordinates CCD File 
DA [auth C],
HA [auth D],
X [auth B]
CHLORIDE ION
Cl
VEXZGXHMUGYJMC-UHFFFAOYSA-M
 Ligand Interaction
Binding Affinity Annotations 
IDSourceBinding Affinity
RC2 BindingDB:  3T3M IC50: min: 95, max: 96 (nM) from 2 assay(s)
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

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Ligand Structure Quality Assessment 



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • 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