Calpain, subdomain III. Calpains are calcium-activated cytoplasmic cysteine proteinases, participate in cytoskeletal remodeling processes, cell differentiation, apoptosis and signal transduction. Catalytic domain and the two calmodulin-like domains are separated by C2-like domain III. Domain III plays an important role in calcium-induced activation of calpain involving electrostatic interactions with subdomain II. Proposed to mediate calpain's interaction with phospholipids and translocation to cytoplasmic/nuclear membranes. CD includes subdomain III of typical and atypical calpains.