Forms a channel through the cell membrane that allows diffusion of 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 open state has a weak anion selectivity whereas the closed state is cation-selective (By similarity). Consists mainly of membrane-spanning sided beta-sheets. Belongs to the eukaryotic mitochondrial porin (TC 1.B.8.1) family.