Expression and characterization of human calpain and calpastatin using baculovirus system

Calpain, the Ca2+-dependent cysteine endopeptidase, and its endogenous inhibitory protein calpastatin are distributed in animal cells and are involved in Ca2+ signalling pathway. Using baculovirus expression system, human mu-calpain with active-site-mutation and calpastatin are expressed and purified. The large subunit of the mutant mu-calpain was processed by the wild type calpain, supporting the intermolecular cleavage mechanism of procalpain during activation. The mutant mu-calpain had no proteolytic activity, but retained the high ordered structure of wild type calpain. The recombinant calpastatin had inhibitory activity for mu- and m-calpain.