Expression, crystallization and preliminary X-ray characterization of the human epithelial cell-adhesion molecule ectodomain.

The epithelial cell-adhesion molecule (EpCAM; CD326) is a transmembrane glycoprotein involved in epithelial cell-cell adhesion, cell proliferation and differentiation. Its elevated expression level in various carcinomas is exploited by several antitumour therapies that are at various stages of clinical development. The 35 kDa polypeptide chain of EpCAM is divided into a large extracellular part, a transmembrane helix and a short cytoplasmic tail. The modular extracellular part of human EpCAM was cloned and mutated to prevent N-linked glycosylation. After expression in insect cells and purification using standard chromatographic techniques, the extracellular part was crystallized. The crystals belonged to space group C2, with unit-cell parameters a = 86.83, b = 50.16, c = 66.56 Å, β = 127.9°. The crystal diffracted to 1.95 Å resolution and contained one molecule in the asymmetric unit.