Crystal structure of human CD22 Ig domains 1-3 in complex with alpha 2-6 sialyllactose

Experimental Data Snapshot

  • Resolution: 2.20 Å
  • R-Value Free: 0.254 
  • R-Value Work: 0.210 
  • R-Value Observed: 0.215 

wwPDB Validation   3D Report Full Report

This is version 2.1 of the entry. See complete history


Molecular basis of human CD22 function and therapeutic targeting.

Ereno-Orbea, J.Sicard, T.Cui, H.Mazhab-Jafari, M.T.Benlekbir, S.Guarne, A.Rubinstein, J.L.Julien, J.P.

(2017) Nat Commun 8: 764-764

  • DOI: https://doi.org/10.1038/s41467-017-00836-6
  • Primary Citation of Related Structures:  
    5VKJ, 5VKK, 5VKM, 5VL3

  • PubMed Abstract: 

    CD22 maintains a baseline level of B-cell inhibition to keep humoral immunity in check. As a B-cell-restricted antigen, CD22 is targeted in therapies against dysregulated B cells that cause autoimmune diseases and blood cancers. Here we report the crystal structure of human CD22 at 2.1 Å resolution, which reveals that specificity for α2-6 sialic acid ligands is dictated by a pre-formed β-hairpin as a unique mode of recognition across sialic acid-binding immunoglobulin-type lectins. The CD22 ectodomain adopts an extended conformation that facilitates concomitant CD22 nanocluster formation on B cells and binding to trans ligands to avert autoimmunity in mammals. We structurally delineate the CD22 site targeted by the therapeutic antibody epratuzumab at 3.1 Å resolution and determine a critical role for CD22 N-linked glycosylation in antibody engagement. Our studies provide molecular insights into mechanisms governing B-cell inhibition and valuable clues for the design of immune modulators in B-cell dysfunction.The B-cell-specific co-receptor CD22 is a therapeutic target for depleting dysregulated B cells. Here the authors structurally characterize the ectodomain of CD22 and present its crystal structure with the bound therapeutic antibody epratuzumab, which gives insights into the mechanism of inhibition of B-cell activation.

  • Organizational Affiliation

    Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON, Canada, M5G 0A4.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
B-cell receptor CD22324Homo sapiensMutation(s): 5 
Gene Names: CD22SIGLEC2
UniProt & NIH Common Fund Data Resources
Find proteins for P20273 (Homo sapiens)
Explore P20273 
Go to UniProtKB:  P20273
PHAROS:  P20273
GTEx:  ENSG00000012124 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP20273
Sequence Annotations
  • Reference Sequence


Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
Glycosylation Resources
GlyTouCan:  G22768VO
GlyCosmos:  G22768VO
GlyGen:  G22768VO
Entity ID: 3
MoleculeChains Length2D Diagram Glycosylation3D Interactions
N-acetyl-alpha-neuraminic acid-(2-6)-beta-D-galactopyranose
Glycosylation Resources
GlyTouCan:  G63069TR
GlyCosmos:  G63069TR
GlyGen:  G63069TR
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on GOL

Download Ideal Coordinates CCD File 
C3 H8 O3
Experimental Data & Validation

Experimental Data

  • Resolution: 2.20 Å
  • R-Value Free: 0.254 
  • R-Value Work: 0.210 
  • R-Value Observed: 0.215 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 124.283α = 90
b = 57.912β = 106.99
c = 48.081γ = 90
Software Package:
Software NamePurpose
XSCALEdata scaling
PDB_EXTRACTdata extraction
XDSdata reduction

Structure Validation

View Full Validation Report

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
CIHR, BantingCanada--

Revision History  (Full details and data files)

  • Version 1.0: 2017-10-04
    Type: Initial release
  • Version 1.1: 2017-10-25
    Changes: Database references
  • Version 1.2: 2019-11-20
    Changes: Data collection, Database references
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Advisory, Atomic model, Data collection, Derived calculations, Structure summary
  • Version 2.1: 2023-10-04
    Changes: Data collection, Database references, Derived calculations, Refinement description, Structure summary