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Unformatted text preview: 553 17.4 Extracellular signals Inactive executioner caspase (zymogen) Cleaved fragments DNA fragmentation Loss of normal cell shape Breakdown of organelles Fragmentation of cell Active executioner caspase Inactivation of DNA endonuclease- sequestering protein Activation of actin-cleaving protein Other targets Cleavage by another caspase Aggregation of executioner caspase subunits Large subunit Small subunit H 2 N COOH Proteolysis of target proteins Figure 17-7 Role of executioner caspases in apoptosis. Cleavage of the zymogen precursor leads to the formation of enzymatically active executioner caspases. As the executioner caspases cleave target proteins, the various cellular breakdown events take place, leading to cell death and removal. enter the nucleus and chop up the cell’s DNA. Another target is a protein that, when cut by the caspases, cleaves actin, a major component of the cytoskeleton. The dis- ruption of actin filaments leads to the loss of normal cell shape. In similar fashion, caspase-activated proteases areshape....
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.
- Spring '08