Has a role in mitochondrial fission. Has a role in outer membrane fission but not matrix separation. Required for targeting MDV1 to the mitochondria. Regulates the assembly of DNM1 into punctate structures, in the mitochondrial tubules, promoting mitochondrial membrane constriction and/or division. Interacts with DNM1 and MDV1. The C-terminus is required for mitochondrial localization, while the N-terminus is necessary for mitochondrial fission. Present with 2410 molecules/cell in log phase SD medium. Belongs to the FIS1 family.