Expression, purification, crystallization and preliminary X-ray analysis of the HER3-9E12 Fab complex.

9E12 is a fully human immunoglobulin G1/κ monoclonal antibody that is specific for the epidermal growth factor receptor 3 (HER3), the overexpression of which has been detected in many tumour types and is associated with poor survival outcomes. To date, knowledge of the molecular mechanism for targeted antibodies that directly inhibit HER3 signalling is limited. Because knowledge of such therapeutic antibodies would help basic immunological therapeutics, structural insights into the HER3-9E12 Fab complex are important. Recombinant human HER3 and Fab fragments of the 9E12 antibody were cloned, expressed and crystallized, and crystallographic data sets were collected. The crystals belonged to space group P1, with unit-cell parameters a=74.4, b=98.6, c=99.6 Å, α=106.0, β=95.0, γ=102.5° and diffracted to a resolution of 2.1 Å.