2AJ3

Crystal Structure of a Cross-Reactive HIV-1 Neutralizing CD4-Binding Site Antibody Fab m18


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.03 Å
  • R-Value Free: 0.269 
  • R-Value Work: 0.225 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Structural mimicry of CD4 by a cross-reactive HIV-1 neutralizing antibody with CDR-H2 and H3 containing unique motifs.

Prabakaran, P.Gan, J.Wu, Y.Q.Zhang, M.Y.Dimitrov, D.S.Ji, X.

(2006) J.Mol.Biol. 357: 82-99

  • DOI: 10.1016/j.jmb.2005.12.062

  • PubMed Abstract: 
  • Human immunodeficiency virus (HIV) entry into cells is initiated by the binding of its envelope glycoprotein (Env) gp120 to receptor CD4. Antibodies that bind to epitopes overlapping the CD4-binding site (CD4bs) on gp120 can prevent HIV entry by comp ...

    Human immunodeficiency virus (HIV) entry into cells is initiated by the binding of its envelope glycoprotein (Env) gp120 to receptor CD4. Antibodies that bind to epitopes overlapping the CD4-binding site (CD4bs) on gp120 can prevent HIV entry by competing with cell-associated CD4; their ability to outcompete CD4 is a major determinant of their neutralizing potency and is proportional to their avidity. The breadth of neutralization and the likelihood of the emergence of antibody-resistant virus are critically dependent on the structure of their epitopes. Because CD4bs is highly conserved, it is reasonable to hypothesize that antibodies closely mimicking CD4 could exhibit relatively broad cross-reactivity and a high probability of preventing the emergence of resistant viruses. Previously, in a search for antibodies that mimic CD4 or the co-receptor, we identified and characterized a broadly cross-reactive HIV-neutralizing CD4bs human monoclonal antibody (hmAb), m18. Here, we describe the crystal structure of Fab m18 at 2.03 A resolution, which reveals unique conformations of heavy chain complementarity-determining regions (CDRs) 2 and 3 (H2 and H3). H2 is highly bulged and lacks cross-linking interstrand hydrogen bonds observed in all four canonical structures. H3 is 17.5 A long and rigid, forming an extended beta-sheet decorated with an alpha-turn motif bearing a phenylalanine-isoleucine fork at the apex. It shows striking similarity to the Ig CDR2-like C'C'' region of the CD4 first domain D1 that dominates the binding of CD4 to gp120. Docking simulations suggest significant similarity between the m18 epitope and the CD4bs on gp120. Fab m18 does not enhance binding of CD4-induced (CD4i) antibodies, nor does it induce CD4-independent fusion mediated by the HIV Env. Thus, vaccine immunogens based on the m18 epitope structure are unlikely to elicit antibodies that could enhance infection. The structure can also serve as a basis for the design of novel, highly efficient inhibitors of HIV entry.


    Organizational Affiliation

    Protein Interactions Group, Center for Cancer Research Nanobiology Program, National Cancer Institute, NIH, Frederick, MD 21702, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Fab m18, Light Chain
A, C, E
213N/AN/A
Protein Feature View is not available: No corresponding UniProt sequence found.
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Fab m18, Heavy Chain
B, D, F
228N/AN/A
Protein Feature View is not available: No corresponding UniProt sequence found.
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
SO4
Query on SO4

Download SDF File 
Download CCD File 
B, D, F
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.03 Å
  • R-Value Free: 0.269 
  • R-Value Work: 0.225 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 48.599α = 90.00
b = 82.620β = 95.27
c = 187.204γ = 90.00
Software Package:
Software NamePurpose
SCALEPACKdata scaling
CNSrefinement
AMoREphasing
HKL-2000data reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2006-03-28
    Type: Initial release
  • Version 1.1: 2008-04-30
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance