The effect of proteasome on myofibrillar structures in bovine skeletal muscle.

When bovine myofibrils are incubated with the 20S proteasome their structure is rapidly damaged with loss of material, particularly from the Z discs and I bands. After 24 hr of incubation the myofibrils rupture and debris appears. Certain myofibrillar proteins, including nebulin, myosin, actin and tropomyosin, are hydrolysed during the incubation; others are solubilised (α-actinin). The 20S proteasome completely and rapidly hydrolyses purified myofibrillar proteins in an energy-independent manner. This shows that the 20S proteasome probably plays a role in the postmortem transformation of muscle and more generally in the hydrolysis of cellular proteins.(1).