Dynamin-related GTPase that is essential for normal mitochondrial morphology by regulating the equilibrium between mitochondrial fusion and mitochondrial fission (PubMed:16778770, PubMed:17709429, PubMed:20185555, PubMed:24616225, PubMed:28746876). Coexpression of isoform 1 with shorter alternative products is required for optimal activity in promoting mitochondrial fusion (PubMed:17709429). Binds lipid membranes enriched in negatively charged phospholipids, such as cardiolipin, and promotes membrane tubulation (PubMed:20185555). The intrinsic GTPase activity is low, and is strongly increased by interaction with lipid membranes (PubMed:20185555). Plays a role in remodeling cristae and the release of cytochrome c during apoptosis (By similarity). Proteolytic processing in response to intrinsic apoptotic signals may lead to disassembly of OPA1 oligomers and release of the caspase activator cytochrome C (CYCS) into the mitochondrial intermembrane space (By similarity). Plays a role in mitochondrial genome maintenance (PubMed:20974897, PubMed:18158317). Inactive form produced by cleavage at S1 position by OMA1 following stress conditions that induce loss of mitochondrial membrane potential, leading to negative regulation of mitochondrial fusion. Isoforms that contain the alternative exon 4b (present in isoform 4 and isoform 5) are required for mitochondrial genome maintenance, possibly by anchoring the mitochondrial nucleoids to the inner mitochondrial membrane. GTP + H2O = GDP + H(+) + phosphate Activated by guanine nucleotide exchange factor RCC1L. Oligomeric complex consisting of membrane-bound and soluble forms of OPA1. Interacts with RCC1L; this interaction is direct (PubMed:28746876). Interacts with CHCHD3 and IMMT; these interactions occur preferentially with soluble OPA1 forms (PubMed:21081504). Binds PARL (By similarity). Interacts with PRELID1 (PubMed:21364629). Detected at contact sites between endoplasmic reticulum and mitochondrion membranes. Additional isoforms seem to exist. Highly expressed in retina. Also expressed in brain, testis, heart and skeletal muscle. Isoform 1 expressed in retina, skeletal muscle, heart, lung, ovary, colon, thyroid gland, leukocytes and fetal brain. Isoform 2 expressed in colon, liver, kidney, thyroid gland and leukocytes. Low levels of all isoforms expressed in a variety of tissues. PARL-dependent proteolytic processing releases an antiapoptotic soluble form not required for mitochondrial fusion. Cleaved by OMA1 at position S1 following stress conditions. Cleavage at position S2 is mediated by YME1L (PubMed:17709429, PubMed:24616225, PubMed:27495975). Cleavage may occur in the sequence motif Leu-Gln-Gln-Gln-Ile-Gln (LQQQIQ) (PubMed:16778770). Cleavage at position S2 is mediated by YME1L (PubMed:17709429, PubMed:24616225, PubMed:27495975). Cleavage may occur in the sequence motif Leu-Gln-Gln-Gln-Ile-Gln (LQQQIQ) (PubMed:16778770). Cleavage at position S2 is mediated by YME1L (PubMed:17709429, PubMed:24616225, PubMed:27495975). Cleavage may occur in the sequence motif Leu-Gln-Gln-Gln-Ile-Gln (LQQQIQ) (PubMed:16778770). The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Contains the alternative exon 4b that is important for mitochondrial genome maintenance. Contains the alternative exon 4b that is important for mitochondrial genome maintenance. Belongs to the TRAFAC class dynamin-like GTPase superfamily. Dynamin/Fzo/YdjA family.