title: Degradation of myofibrillar proteins by trypsin-like serine proteinases.
abstract: The effects of the Ca2+-activated cysteine proteinase, the rat trypsin-like serine proteinase and bovine trypsin on myofibrillar proteins from rabbit skeletal muscle are compared. 2. Myofibrils that had been treated at neutral pH with the Ca2+-dependent proteinase and with the rat enzyme were (a) analyzed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and (b) examined in the electron microscope. Treatment with each proteinase resulted in the loss of the Z-discs, but the rat enzyme caused much more extensive disruption of the ultrastructure and degraded more of the myofibrillar proteins. 3. Purified F-actin was almost totally resistant to the proteinases, whereas G-actin was degraded by the rat trypsin-like proteinase at a rate approx. 15 times faster than was obtained with bovine trypsin. 4. Similar results were obtained with alpha-actinin, whereas tropomyosin was degraded more readily by bovine trypsin than by the rat trypsin-like proteinase. 5. The implications of these findings for the non-lysosomal breakdown of myofibrillar proteins in vivo are considered.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003546:Cysteine Endopeptidases; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000378:metabolism*; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D009124:Muscle Proteins / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism* / Q000648:ultrastructure; D011817:Rabbits; D012697:Serine Endopeptidases; D014357:Trypsin / Q000378:metabolism
chemical_list: D009124:Muscle Proteins; D010450:Endopeptidases; D012697:Serine Endopeptidases; D014357:Trypsin; D003546:Cysteine Endopeptidases; D002118:Calcium