Purification and some properties of a Ca2+-activated muscle enzyme that removes Z-disks

Localization of [alpha]-actinin and tropomyosin in muscle and nonmuscle systems

“…CAF-treatment of IZI brushes followed by washing the CAF-treated brushes once in distilled H2O at 22°C (see Materials and Methods) almost completely removes all amorphous, densely staining material from the brushes (Figure 90). Dayton (1974) has shown that CAF-treatment under these conditions removes almost all a-actinin from IZI brushes. The CAF-treated residue consists largely of randomly oriented filaments, although occasionally aggregates of thin filaments that resemble remnants of the Z-disk lattice are observed ( Figure 90).…”

“…It may be suggested that the simple interaction of a-actinin with actin changes the conformation of one or both these proteins to make them susceptible to proteolysis by CAF. Purified CAF, however, is unable to liberate a-actinin from the a-actinin/F-actin complex formed by mixing purified a-actinin and purified fibrous actin in vitro (Dayton, 1974). Indeed, neither a-actinin nor actin in such a complex is altered by even prolonged incubation with CAF (Dayton, 1974).…”

“…The discovery (Busch et al, 1972), purification (Dayton, 1974;Dayton et al, 1976a) and characterization (Dayton ^ , 1975(Dayton ^ , , 1976a 2+ of a Ca -activated proteolytic enzyme (CAP) that very quickly removes Z-disks but that has very limited and specific effects on the myofibrillar proteins permitted some studies using this protease as a molecular probe of Z-disk architecture. The results of these experiments were very surprising and may have important consequences for ideas aborir the a-actinin/F-actin Interaction and Z-disk structure.…”

“…The results of these experiments were very surprising and may have important consequences for ideas aborir the a-actinin/F-actin Interaction and Z-disk structure. Incubation of CAE with myofibrils results in complete removal of Z-disks and of the 38.5-nm periodicity associated with the presence of troponin along the thin filament (Dayton, 1974 ;Dayton _et a^. , 1975Dayton _et a^.…”