Crystallization and preliminary X‐ray diffraction analysis of the complex of a human anti‐ephrin type‐A receptor 2 antibody fragment and its cognate antigen
The recombinant N‐terminal domain of human ephrin type‐A receptor 2 (rEphA2) has been crystallized in complex with the recombinantly produced Fab fragment of a fully human antibody (1C1; IgG1/κ). These are the first reported crystals of an ephrin receptor bound to an antibody. The orthorhombic crystals belonged to space group C2221 (the 00l reflections obey the l = 2n rule), with unit‐cell parameters a = 78.93, b = 120.79, c = 286.20 Å. The diffraction of the crystals extended to 2.0 Å resolution. However, only data to 2.55 Å resolution were considered to be useful owing to spot overlap caused by the long unit‐cell parameter. The asymmetric unit is most likely to contain two 1C1 Fab–rEphA2 complexes. This corresponds to a crystal volume per protein weight (V M) of 2.4 Å3 Da−1 and a solvent content of 49.5%. The three‐dimensional structure of this complex will shed light on the molecular basis of 1C1 specificity. This will also contribute to a better understanding of the mechanism of action of this antibody, the current evaluation of which as an antibody–drug conjugate in cancer therapy makes it a particularly interesting case study.
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