Involved in mitochondrial fission. Has a partially redundant function to CAF4 in acting as an adapter protein, binding to FIS1 on the mitochondrial outer membrane and recruiting the dynamin-like GTPase DNM1 to form mitochondrial fission complexes. Formation of these complexes is required to promote constriction and fission of the mitochondrial compartment at a late step in mitochondrial division (By similarity). Interacts with CAF4, DNM1 and FIS1, components of the mitochondrial fission machinery. Interacts via its N-terminal, coiled-coil extension (NTE) with FIS1, and via its WD repeats with DNM1 (By similarity). Uniformly distributed on the cytoplasmic face of the mitochondrial outer membrane. This localization is dependent on FIS1. Reorganizes to punctate structures on mitochondria, corresponding to mitochondrial constriction sites, at a late step in mitochondrial division. This relocalization is dependent on DNM1 (By similarity). Belongs to the WD repeat MDV1/CAF4 family.