Treatment of isolated myofibrils with Ca2+-activated neutral proteinase (CANP) results in specific removal of Z-line and of alpha-actinin. To investigate the ionic requirement for these processes, we measured Z-line removal by phase-contrast and interference microscopy and alpha-actinin removal by sodium dodecyl sulphate/polyacrylamide-gel electrophoretic analysis of myofibrillar proteins. The proteolytic digestion of native purified proteins was measured directly on polyacrylamide gels and by the fluorescamine technique. We found that the removal of Z-line and alpha-actinin as well as the release of proteolytic degradation products from isolated myofibrils by CANP occur only in the presence of Ca2+; Sr2+, Ba2+, Mn2+, Mg2+, Co2+ and Zn2+ are all ineffective. In contrast with this stringent requirement for Ca2+, the proteolytic activity of CANP measured with denatured casein, native and denatured haemoglobin, native actin and tropomyosin also occurs in the presence of other bivalent cations, in the following order: Ca2+ greater than Sr2+ greater than Ba2+. These data suggest that only Ca2+ can produce the conformational change in myofibrils that renders them susceptible to the action of CANP, whereas its proteolytic activity is stimulated by several bivalent ions.
Stringent requirement for Ca2+ in the removal of Z-lines and α-actinin from isolated myofibrils by Ca2+-activated neutral proteinase
- Views Icon Views
- Share Icon Share
M K Reddy, M Rabinowitz, R Zak; Stringent requirement for Ca2+ in the removal of Z-lines and α-actinin from isolated myofibrils by Ca2+-activated neutral proteinase. Biochem J 1 March 1983; 209 (3): 635–641. doi: https://doi.org/10.1042/bj2090635
Download citation file: