Action of Calpain on α-Actinin within and Isolated from Carp Myofibrils

Abstract

When purified α-actinin from carp ordinary muscle was treated with calpain type II from the same muscle, SDS-PAGE revealed that α-actinin subunits were cloven into fragments of slightly lower molecular mass. On Sephacryl S-300 gel filtration, however, calpain-treated α-actinin was eluted at the same position as that of the native one, suggesting that the dimeric subunit composition still remained after calpain digestion under the physiological condition. The binding ability of α-actinin to F-actin at low temperature was slightly increased by calpain treatment.
It was also found that calpain clove not only isolated α-actinin but also α-actinin within carp myofibrils. In addition calpain showed an another function to solubilize and release both native and digested α-actinins from the myofibrils.
These results suggested that α-actinin removing action of calpain rather than α-actinin cleavage would be expected to contribute to the weakening of Z-line.