Purification and spectroscopic characterization of a recombinant amino-terminal polypeptide fragment of mouse epithelial cadherin

Cadherins are a family of Ca2+-dependent cell adhesion molecules containing four extracellular tandem repeats each of 110 amino acids. The most amino-terminal repeat is believed to confer the specificity of cell adhesion. A polypeptide containing the amino-terminal repeat of mouse epithelial cadherin has been over-expressed in E. coli and purified to homogeneity. This polypeptide binds Ca2+ with a dissociation constant of 1.6 × 10−4M. CD and NMR experiments indicate that the polypeptide adopts a predominantly β-sheet conformation and that binding of Ca2+ induces only small conformational changes.