VDAC2 is a voltage dependent anion channel that mediates the flow of metabolites and ions across the outer mitochondrial membrane. It may play a role in mitochondrial apoptosis through its involvement in the mitochondrial recruitment of BAK, a protein belonging to the BCL-2 protein family [, , ].Voltage dependent anion channels (VDACs) or porins by analogy with bacterial porins, are pore-forming proteins associated with mitochondria, although they are also present in the endoplasmic reticulum (ER) []and plasma membrane []. In mammals, three VDAC isoforms have been identified: VDAC1 to 3. They have a very similar predicted structure, consisting of a 19 amphipathic β-strands barrel with an N-terminal α-helix in the central pore [, ]. The channel opening faces both the cytosol and mitochondrial intermembrane space [, ]. They play a major role in cellular energetic metabolism due to its ability to allow the exchange of molecules between the cytosol and the mitochondrial intermembrane space. They may also play a role in cell death. However, several mouse gene knock out studies show that VDACs are dispensable for both MPT (mitochondrial permeability transition) and Bcl-2 family member-driven cell death [, ].
Eukaryotic mitochondrial porins are voltage-dependent anion-selective channels (VDAC) that behave as general diffusion pores for small hydrophilic molecules [, , , ]. The channel adopts an open conformation at low or zero membrane potential and a closed conformation at potentials above 30-40 mV.The proteins are composed of between 12 to 16 β-strands that span the mitochondrial outer membrane. Yeast contains two members of this family (genes POR1 and POR2); vertebrates have at least three members (genes VDAC1, VDAC2 and VDAC3) [, ].
This entry represents both eukaryotic mitochondrial porins and Tom40 proteins.Eukaryotic mitochondrial porins are voltage-dependent anion-selective channels (VDAC) that behave as general diffusion pores for small hydrophilic molecules [, , , ]. The channels adopt an open conformation at low or zero membrane potential and a closed conformation at potentials above 30-40 mV. The eukaryotic mitochondrial porins are β-barrel proteins, composed of between 12 to 16 β-strands that span the mitochondrial outer membrane. Yeast contains two members of this family (genes POR1 and POR2); vertebrates have at least three members (genes VDAC1, VDAC2 and VDAC3) []. They are related to the mitochondrial import receptor subunit Tom40 proteins, sharing a common evolutionary origin and structure [].Tom40 is a mitochondrion outer membrane protein and a component of the TOM (translocator of the outer mitochondrial membrane) complex, which is essential for import of protein precursors into mitochondria []. In Saccharomyces cerevisiae, TOM complex is composed of the subunits Tom70, Tom40, Tom22, Tom20, Tom7, Tom6, and Tom5 [, ]. Tom40 is an integral membrane protein and the main structural component of the protein-conducting channel formed by the TOM complex []. It is stabilised by other components, such as Tom5, Tom6, and Tom7 [].
