Engineering the Fab fragment of the anti-IgE omalizumab to prevent Fab crystallization and permit IgE-Fc complex crystallization

Structure of the omalizumab Fab.

Omalizumab is a humanized anti-IgE antibody that inhibits the binding of IgE to its receptors on mast cells and basophils, thus blocking the IgE-mediated release of inflammatory mediators from these cells. Omalizumab binds to the Fc domains of IgE in proximity to the binding site of the high-affinity IgE receptor FcℇRI, but the epitope and the mechanisms and conformations governing the recognit...

Fab-mediated Crystallization of a Potassium Channel

Preparation, characterization and crystallization of an antibody Fab fragment that recognizes RNA. Crystal structures of native Fab and three Fab-mononucleotide complexes.

Fab fragments from Jel 103, an antibody which specifically binds to single-stranded poly(rl), were prepared by papain digestion, separated into eight isoforms and characterized by mass spectrometry. One of the purified isoforms yielded crystals suitable for structural studies by X-ray diffraction and its crystal structure was determined to 2.4 A resolution. Soaking the crystals in solutions con...

Crystallization with hapten of the Fab' fragment from a mouse IgA myeloma protein with antidinitrophenyl activity.

Protein 315, a mouse myeloma IgA protein which binds nitrophenyl ligands, and its pepsin-produced Fab’ fragment have been purified by affinity chromatography. The Fab’ fragments were found to be homogeneous by polyacrylamide electrophoresis and isoelectric focusing, and to possess a uniform binding constant. These fragments were readily crystallizable at low salt concentration near their isoele...

Structural basis of omalizumab therapy and omalizumab-mediated IgE exchange

Omalizumab is a widely used therapeutic anti-IgE antibody. Here we report the crystal structure of the omalizumab-Fab in complex with an IgE-Fc fragment. This structure reveals the mechanism of omalizumab-mediated inhibition of IgE interactions with both high- and low-affinity IgE receptors, and explains why omalizumab selectively binds free IgE. The structure of the complex also provides mecha...