m-Calpain activation in vitro does not require autolysis or subunit dissociation.

摘要: Abstract Calpains are Ca2+-dependent, intracellular cysteine proteases involved in many physiological functions. How calpains activated the cell is unknown because average concentration of Ca2+ orders magnitude lower than that needed for half-maximal activation enzyme vitro. Two proposed mechanisms by which can overcome this differential autoproteolysis (autolysis) and subunit dissociation, both could release constraints on core breaking link between anchor helix small to allow active site form. By measuring rate autolysis at different sites calpain, we show while one first targets be cut, occurs same time-frame as several potentially inactivating cleavages Domain III. Thus autolytic would overlap with inactivation. We also does not dissociate from large subunit, but proteolyzed a 40–45 k heterodimer Domains IV VI. It likely autolysis-generated has previously been misidentified homodimer produced dissociation. propose model m-calpain involve either or