Mitofusin-1 (MFN1) is a mediator of mitochondrial fusion.This protein and mitofusin 2 are homologs of the Drosophila protein fuzzy onion (Fzo).Mitofusins are large predicted GTPases located in outer mitochondrial membrane.They are essential for outer membrane fusion by interacting with each other to facilitate mitochondrial targeting.The mitofusins are the first known protein mediator of mitochondrial fusion, and mediate developmentally regulated post-meiotic fusion of mitochondria.