Essential transmembrane GTPase, which mediates mitochondrial fusion. Fusion of mitochondria occurs in many cell types and constitutes an important step in mitochondria morphology, which is balanced between fusion and fission. MFN1 acts independently of the cytoskeleton. Overexpression induces the formation of mitochondrial networks. Belongs to the mitofusin family. 3 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.