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  • Open Access

Procaspase-9 is attached to the mitochondrial outer membrane in the early stages of apoptosis

Cellular & Molecular Biology LettersAn International Journal200712:20

  • Received: 31 January 2007
  • Accepted: 2 March 2007
  • Published:


Procaspase-9 is the zymogen form of one of the apoptosis initiators, caspase-9. Its cellular location may differ depending on the cell type; it is found throughout the cytosol, although some of it may be associated with the mitochondria. Procaspase-9 relocates from the cytosol to the mitochondria shortly after the triggering of apoptosis in rat hepatocytes. We investigated whether the mitochondrial protein import machineries import procaspase-9. The combined results of protein import analyses, mitochondrial fractionation and protease treatments of intact and swollen mitochondria imply that procaspase-9 attaches to the outer surface of the mitochondrial outer membrane.

Key words

  • Caspase-9
  • Procaspase-9
  • Mitochondria
  • Apoptosis
  • Protein import
  • Rotenone
  • Localization