STRUCTURE OF A CALPAIN CA2-BINDING DOMAIN REVEALS A NOVEL EF-HAND ANDCA2+-INDUCED CONFORMATIONAL-CHANGES()

The crystal structure of a Ca2+-binding domain (dVI) of rat m-calpain has been determined at 2.3 Angstrom resolution, both with and without bound Ca2+. The structures reveal a unique fold incorporating five EF- hand motifs per monomer, three of which bind calcium at physiological calcium concentrations, with one showing a novel EF-hand coordination pattern. This investigation gives us a first view of the calcium-induc ed conformational changes, and consequently an insight into the mechan ism of calcium induced activation in calpain. The crystal structures r eveal a dVI homodimer which provides a preliminary model for the subun it dimerization in calpain.