Calpains are a family of non-lysosomal cysteine proteases that are activated by calcium. Calcium-dependent protease activity has already been detected in 1964 in brain tissue from rats, and this activity was later related to calpain. Yet, the identification of the protein started off with structural analysis of muscle tissue and its alteration by post mortem degradation (history broadly reviewed by Goll et al. 1990, 2003): In the late 1960s, Wayne Busch and Darrel Goll studied the physiological effects of Ca2+ in tissue specimen of rabbit muscle. When muscle strips were left overnight in a 1 mM Ca2+buffer solution, it became apparent that the Z-line (a structural element separating sarcomers in skeletal muscle) had completely disappeared. Busch and Goll subsequently incubated the stripes in EGTA, thereby preventing degradation of the Z-line. With the help...
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