Oxidized or Reduced Cytochrome c and Axial Ligand Variants All Form the Apoptosome in Vitro

Deanna L. Mendez, Ildikó V. Akey, Christopher W. Akey, Robert G. Kranz

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Cytochrome c (cyt c) has two important roles in vertebrates: mitochondrial electron transport and activating the intrinsic cell death pathway (apoptosis). To initiate cell death, cyt c dissociates from the inner mitochondrial membrane and migrates to the cytosol. In the cytosol, cyt c interacts stoichiometrically with apoptotic protease activating factor 1 (Apaf-1) and upon ATP binding induces formation of the heptameric apoptosome. It is not clear however what the redox state of cyt c is when it functions as the "active signal" for apoptosis. Some reports have indicated that only ferri (i.e., oxidized Fe3+ heme) but not ferro (reduced, Fe2+ heme) cyt c forms the apoptosome. Facilitated by our recently described recombinant system for synthesizing novel human cyt c proteins, we use a panel of cyt c axial ligand variants that exhibit a broad range of redox potentials. These variants exist in different redox states. Here we show that cyt c wild type and cyt c H19M (reduced state) and cyt c M81A and cyt c M81H (oxidized state) all bind to Apaf-1 and form the apoptosome.

Original languageEnglish
Pages (from-to)2766-2769
Number of pages4
Issue number22
StatePublished - Jun 6 2017


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