Crystallization and preliminary X-ray crystallographic studies on a Fab fragment of the mouse anti-human Fas monoclonal antibody HFE7A

The Fas-Fas ligand system is involved in apoptosis. The mouse anti-human Fas monoclonal antibody HFE7A (m-HFE7A) has a potential use in human therapy against autoimmune diseases such as rheumatoid arthritis. Information on the three-dimensional structure is essential for antibody humanization. Crystals of an antigen-binding fragment (Fab) of m-HFE7A were obtained by the hanging-drop vapour-diffusion method using sodium citrate as a precipitant and 2-­methyl-2,4-pentanediol as an additive. Fast optimization to produce single crystals suitable for X-ray analysis was achieved by the streak-seeding technique. The crystals belong to the orthorhombic space group P2₁2₁2₁, with unit-cell parameters a = 43.4, b = 74.0, c = 133.8 Å. The crystals diffract at least to 2.5 Å resolution.