PREFERENCE OF CALCIUM-DEPENDENT INTERACTIONS BETWEEN CALMODULIN-LIKE DOMAINS OF CALPAIN AND CALPASTATIN SUBDOMAINS

Calpastatin molecule contains four repeated inhibition domains, each h aving highly conserved internal regions A, B and C. The synthetic olig opeptides of regions A and C had no calpain inhibition activity while region B oligopeptide shelved weak inhibition activity. Real-time biom olecular interaction analysis using a BIAcore instrument revealed that the bacterially expressed calmodulin-like domain of the calpain large subunit (L-CaMLD) and that of the small subunit (S-CaMLD) interacted, in a Ca2+-dependent fashion, preferentially with the immobilized synt hetic oligopeptide of region A and that of region C, respectively. Cal modulin showed no specific binding to these oligopeptides. The tripart ite structure of the calpastatin functional domain may confer the spec ific interactions with the protease domain and the two CaMLDs of calpa in.