Voltage-dependent anion-selective channel (VDAC1) (also referred to as porin, isoform 1) is a small protein, originally discovered in the outer membrane of mitochondria where it constitutes the major pore-forming protein. The porin protein VDAC1 allows to the outer-most membrane of the mitochondrion free permeability to low molecular-weight solutes. VDAC1 has been shown to co-immunoprecipitate with the anti-apoptotic protein Bcl-2 and suggested to be involved in forming the mitochondrial pore which releases cytochrome c during apoptosis.