... PAGE and immunoblot analysis of differentially tagged calpain 1 and 2 heterodimers. (A) Lane 1: molecular mass standards indi-cated at the side of the gel. Lanes 2, 3 and 4: flow-through, wash and ... pathologies may facilitatetreatment of these diseases.The ubiquitous and well-characterized members of the family, calpains 1 and 2 (l-isoform and m-isoform,respectively), are heterodimers, ... the natural inhibitor of calpains 1 and 2 [32], binds to sites on the PEFdomains of both the large and small subunits [33,34].In the presence of Ca2+, subdomains A and C of calpastatin tightly...