4EJ1

Binding of Nb113 camelid antibody fragment with the binary DHFR:folate complex


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.75 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.186 
  • R-Value Observed: 0.188 

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Ligand Structure Quality Assessment 


This is version 1.3 of the entry. See complete history


Literature

Mechanistic analysis of allosteric and non-allosteric effects arising from nanobody binding to two epitopes of the dihyrofolate reductase of Escherichia coli.

Oyen, D.Wechselberger, R.Srinivasan, V.Steyaert, J.Barlow, J.N.

(2013) Biochim Biophys Acta 1834: 2147-2157

  • DOI: https://doi.org/10.1016/j.bbapap.2013.07.010
  • Primary Citation of Related Structures:  
    4EIG, 4EIZ, 4EJ1, 4FHB

  • PubMed Abstract: 

    Although allosteric effector antibodies are used widely as modulators of receptors and enzymes, experimental analysis of their mechanism remains highly challenging. Here, we investigate the molecular mechanisms of allosteric and non-allosteric effector antibodies in an experimentally tractable system, consisting of single-domain antibodies (nanobodies) that target the model enzyme dihydrofolate reductase (DHFR) from Escherichia coli. A panel of thirty-five nanobodies was isolated using several strategies to increase nanobody diversity. The nanobodies exhibit a variety of effector properties, including partial inhibition, strong inhibition and stimulation of DHFR activity. Despite these diverse effector properties, chemical shift perturbation NMR epitope mapping identified only two epitope regions: epitope α is a new allosteric site that is over 10Å from the active site, while epitope β is located in the region of the Met20 loop. The structural basis for DHFR allosteric inhibition or activation upon nanobody binding to the α epitope was examined by solving the crystal structures of DHFR in complex with Nb113 (an allosteric inhibitor) and Nb179 (an allosteric activator). The structures suggest roles for conformational constraint and altered protein dynamics, but not epitope distortion, in the observed allosteric effects. The crystal structure of a β epitope region binder (ca1698) in complex with DHFR is also reported. Although CDR3 of ca1698 occupies the substrate binding site, ca1698 displays linear mixed inhibition kinetics instead of simple competitive inhibition kinetics. Two mechanisms are proposed to account for this apparent anomaly. Evidence for structural convergence of ca1698 and Nb216 during affinity maturation is also presented.


  • Organizational Affiliation

    Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium; Structural Biology Research Centre, VIB, Pleinlaan 2, 1050 Brussels, Belgium.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Dihydrofolate reductase
A, B
159Escherichia coli K-12Mutation(s): 0 
Gene Names: folAtmrAb0048JW0047
EC: 1.5.1.3
UniProt
Find proteins for P0ABQ4 (Escherichia coli (strain K12))
Explore P0ABQ4 
Go to UniProtKB:  P0ABQ4
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP0ABQ4
Sequence Annotations
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  • Reference Sequence
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Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
Nb113 camelid antibody fragment
C, D
134Lama glamaMutation(s): 0 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.75 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.186 
  • R-Value Observed: 0.188 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 100.741α = 90
b = 77.064β = 92
c = 92.777γ = 90
Software Package:
Software NamePurpose
ADSCdata collection
PHASERphasing
PHENIXrefinement
DENZOdata reduction
SCALEPACKdata 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: 2013-04-24
    Type: Initial release
  • Version 1.1: 2013-08-14
    Changes: Database references
  • Version 1.2: 2013-09-04
    Changes: Database references
  • Version 1.3: 2013-10-30
    Changes: Derived calculations