Mitochondrial outer membrane protein involved in the regulation of mitochondrial organization (PubMed:29361167). It is required for mitochondrial fission and promotes the recruitment and association of the fission mediator dynamin-related protein 1 (DNM1L) to the mitochondrial surface independently of the mitochondrial fission FIS1 and MFF proteins. Regulates DNM1L GTPase activity. {ECO:0000269|PubMed:21508961, ECO:0000269|PubMed:23283981, ECO:0000269|PubMed:23530241, ECO:0000269|PubMed:23921378, ECO:0000269|PubMed:29361167, ECO:0000269|PubMed:29899447}. This is the function of MIEF2 (mitochondrial elongation factor 2, ENSG00000177427).