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


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.





mitochondrial processing peptidase


oxidase assembly complex


proteinase K


phenylmethyl sulfonyl fluoride


targeting sequence of subunit 9 of F0F1-ATPase


sorting and assembly machinery


sodium dodecyl sulfate-polyacrylamide gel electrophoresis


translocase of the inner membrane


topogenesis of the outer membrane


translocase of the outer membrane




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Correspondence to Irina Milisav.

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Milisav, I., Šuput, D. Procaspase-9 is attached to the mitochondrial outer membrane in the early stages of apoptosis. Cell Mol Biol Lett 12, 509–522 (2007).

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Key words

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