Involved in the fragmentation of the mitochondrial network and its perinuclear clustering. Plays a minor role in the recruitment and association of the fission mediator dynamin-related protein 1 (DNM1L) to the mitochondrial surface and mitochondrial fission. Can induce cytochrome c release from the mitochondrion to the cytosol, ultimately leading to apoptosis (By similarity). Interacts with DNM1L/DLP1 through the TPR region. Interacts with MARCH5. Interacts with MIEF1. Interacts with PEX11A, PEX11B and PEX11G. The C-terminus is required for mitochondrial localization, while the N-terminus is necessary for mitochondrial fission. Ubiquitinated by MARCH5. Belongs to the FIS1 family.