The voltage-dependent anion channel (VDAC) plays a central role in apoptosis, participating in the release of apoptogenic factors such as cytochrome c. The molecular mechanisms by which VDAC forms a protein-conducting channel for the passage of cytochrome c are unclear. The present work approaches this problem by addressing the oligomeric status of VDAC and its role in the release of cytochrome c. Chemical cross-linking of isolated mitochondria or purified VDAC fixed VDAC into dimers to tetramers. Fluorescence Resonance Energy Transfer between differentially labeled VDAC further supports VDAC oligomerization. Mitochondrial cross-linking prevented both PTP opening and release of cytochrome c, yet had no effect on electron transport or Ca2 + uptake. Cross-linking had no effect on the channel properties of bilayer-reconstituted purified VDAC, but inhibited release of encapsulated cytochrome c within VDAC-proteoliposomes or via bilayer-reconstituted VDAC. Moreover, encapsulated but not soluble cytochrome c induced VDAC oligomerization. These results suggest cytochrome c- induced VDAC oligomerization as a novel mechanism for cytochrome c crossing the outer mitochondria membrane, with transfer occurring via the large flexible pore formed between individual subunits of a VDAC oligomer.
|Number of pages
|Biochimica et Biophysica Acta (BBA) - Bioenergetics
|Published - Jun 2004
|13th European Bioenergetics Conference - Pisa, Italy
Duration: 21 Aug 2004 → 24 Aug 2004