3PP3 image
Deposition Date 2010-11-24
Release Date 2011-04-13
Last Version Date 2024-11-06
Entry Detail
PDB ID:
3PP3
Keywords:
Title:
Epitope characterization and crystal structure of GA101 provide insights into the molecular basis for the type I / type II distinction of anti- CD20 antibodies
Biological Source:
Source Organism:
Mus musculus (Taxon ID: 10090)
Host Organism:
Method Details:
Experimental Method:
Resolution:
2.51 Å
R-Value Free:
0.26
R-Value Work:
0.20
R-Value Observed:
0.21
Space Group:
C 1 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:GA101 Fab heavy chain
Chain IDs:A (auth: H), C (auth: I)
Chain Length:224
Number of Molecules:2
Biological Source:Mus musculus
Polymer Type:polypeptide(L)
Molecule:GA101 Fab light chain
Chain IDs:B (auth: L), D (auth: K)
Chain Length:219
Number of Molecules:2
Biological Source:Mus musculus
Primary Citation
Epitope characterization and crystal structure of GA101 provide insights into the molecular basis for type I/II distinction of CD20 antibodies.
Blood 118 358 367 (2011)
PMID: 21444918 DOI: 10.1182/blood-2010-09-305847

Abstact

CD20 is a cell-surface marker of normal and malignant B cells. Rituximab, a monoclonal antibody targeting CD20, has improved the treatment of malignant lymphomas. Therapeutic CD20 antibodies are classified as either type I or II based on different mechanisms of killing malignant B cells. To reveal the molecular basis of this distinction, we fine-mapped the epitopes recognized by both types. We also determined the first X-ray structure of a type II antibody by crystallizing the obinutuzumab (GA101) Fab fragment alone and in complex with a CD20 cyclopeptide. Despite recognizing an overlapping epitope, GA101 binds CD20 in a completely different orientation than type I antibodies. Moreover, the elbow angle of GA101 is almost 30° wider than in type I antibodies, potentially resulting in different spatial arrangements of 2 CD20 molecules bound to a single GA101 or rituximab molecule. Using protein tomography, different CD20 complexes were found to be associated with the 2 antibodies, and confocal microscopy showed different membrane compartmentalization of these subpopulations of the cellular CD20 pool. Our findings offer a possible molecular explanation for the different cellular responses elicited by type I and II antibodies.

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