Fig. 2. Schematic representation of mitochondrial fusion and fission events. During fusion mitofusin 1 or 2 (Mfn1/2) proteins link two juxtaposed mitochondria through their coiled-coil domains. This is followed by outer, and subsequently inner, membrane fusion, which is GTP dependent and regulated by Opa1. During fission, Dnm1l is recruited from the cytosol to the outer mitochondrial membrane, where it interacts directly or indirectly with Fis1, leading to constriction of mitochondria and sequential separation of the inner and outer membrane.