Calpain-3 associates with protein complexes in the SR.
IP of microsomal fractions with anti-pIS2C antibody analyzed by western blot using antibodies against RyR (A), SERCA1a (B), CSQ1(C), junctin (D), triadin (E), DHPRα1 (F) and DHPRβ1 (G). Peptide-absorbed anti-calpain-3 (pIS2C) antibody (abs-anti-pIS2C) and normal mouse sera were used as negative controls. Junctin is one of the isoforms of aspartyl/asparaginyl α-hydroxylase (ASPH). Apparent molecular weight of junctin is about 40,000, although its calculated molecular weight is 26,000.37 Closed arrowheads, indicated proteins; IB, immunoblot; skm, total muscle fractions as a positive control for RyR; SR, microsome fraction as a positive control for junctin and triadin; *non-specific band detected by anti-triadin antibody used.