From Proteopediaproteopedia link
Crystal structure of Rituximab Fab in complex with an epitope peptide
[CD20_HUMAN] Defects in MS4A1 are the cause of immunodeficiency common variable type 5 (CVID5) [MIM:613495]; also called antibody deficiency due to CD20 defect. CVID5 is a primary immunodeficiency characterized by antibody deficiency, hypogammaglobulinemia, recurrent bacterial infections and an inability to mount an antibody response to antigen. The defect results from a failure of B-cell differentiation and impaired secretion of immunoglobulins; the numbers of circulating B-cells is usually in the normal range, but can be low.
[CD20_HUMAN] This protein may be involved in the regulation of B-cell activation and proliferation.
Publication Abstract from PubMed
Rituximab is a widely used monoclonal antibody drug for treating certain lymphomas and autoimmune diseases. To understand the molecular mechanism of recognition of human CD20 by Rituximab, we determined the crystal structure of the Rituximab Fab in complex with a synthesized peptide comprising the CD20 epitope (residues 163-187) at 2.6-A resolution. The combining site of the Fab consists of four complementarity determining regions that form a large, deep pocket to accommodate the epitope peptide. The bound peptide assumes a unique cyclic conformation that is constrained by a disulfide bond and a rigid proline residue (Pro(172)). The (170)ANPS(173) motif of CD20 is deeply embedded into the pocket on the antibody surface and plays an essential role in the recognition and binding of Rituximab. The antigen-antibody interactions involve both hydrogen bonds and van der Waals contacts and display a high degree of structural and chemical complementarity. These results provide a molecular basis for the specific recognition of CD20 by Rituximab as well as valuable information for development of improved antibody drugs with better specificity and higher affinity.
Structural basis for recognition of CD20 by therapeutic antibody Rituximab.,Du J, Wang H, Zhong C, Peng B, Zhang M, Li B, Huo S, Guo Y, Ding J J Biol Chem. 2007 May 18;282(20):15073-80. Epub 2007 Mar 29. PMID:17395584
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.