Figure 5. A structural model for an oligomeric Bax pore in the mitochondrial outer membrane.

• A
  As demonstrated by our study and shown in the model, Bax core dimers form parts of the proteolipid wall that separates the nonpolar membrane from the aqueous pore. Other regions of the Bax oligomer and radially arranged lipids may form other parts of the wall. The diameter of the pore will be determined by the stoichiometry of the Bax oligomer and the number of the radially arranged lipids.
• B
  In order to release a hydrated cytochrome c from the mitochondria, the diameter of the pore must be > 60 Å, the diameter of cytochrome c plus a water shell. The length of a core dimer along its longest axis (L) = 45 Å. Since the axis tilts 60° from the bilayer normal, a core dimer can cover 39 Å of the lipid bilayer around the pore (M). Assume the pore diameter = 60 Å, and the pore wall only consists of Bax core dimers, six Bax core dimers or 12 Bax proteins are required to form a hexagonal pore that can release cytochrome c. The structure of cytochrome C in the pore was generated from PDB file 3ZCF using PyMOL program.