title: Calcium-dependent proteolysis of calcium-binding proteins.
abstract: In several myopathic disorders, the internal muscle cell calcium concentration increases significantly as compared to normal muscle cells. We report that in the presence of elevated calcium levels, the calcium-binding proteins troponin C and calmodulin are protected from digestion by the chymotrypsin-like serine proteinase that co-purifies with isolated myofibrils. Degradation of the 67k calcimedin in the presence of calcium shows altered major cleavage fragments while degradation of myosin is unaffected by the presence of calcium. A role for this serine proteinase in muscle-wasting diseases is suggested.
mesh_terms: D000818:Animals; D017317:Annexin A6; D017302:Annexins; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D002384:Catalysis; D010450:Endopeptidases / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000201:enzymology; D009218:Myosins / Q000378:metabolism; D051381:Rats; D012697:Serine Endopeptidases; D014336:Troponin / Q000378:metabolism; D019209:Troponin C
chemical_list: D017317:Annexin A6; D017302:Annexins; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D014336:Troponin; D019209:Troponin C; D010450:Endopeptidases; D012697:Serine Endopeptidases; D009218:Myosins; D002118:Calcium