The effect of proteasome on myofibrillar structures in bovine skeletal muscle

When bovine myofibrils are incubated with the 20S proteasome their structur e is rapidly damaged with loss of material, particularly from the Z discs a nd I bands. After 24 hr of incubation the myofibrils rupture and debris app ears. Certain myofibrillar proteins, including nebulin, myosin, actin and t ropomyosin, are hydrolysed during the incubation; others are solubilised (a lpha-actinin). The 20S proteasome completely and rapidly hydrolyses purifie d myofibrillar proteins in an energy-independent manner. This shows that th e 20S proteasome probably plays a role in the postmortem transformation of muscle and more generally in the hydrolysis of cellular proteins. (C) 1998 Elsevier Science Ltd. All rights reserved.