This gene product is a nuclear-encoded mitochondrial protein with similarity to dynamin-related GTPases. It is a component of the mitochondrial network. The OPA1 protein localizes to the inner mitochondrial membrane, where it regulates mitochondrial fusion and cristae structure. OPA1 mediates mitochondrial fusion in cooperation with mitofusins 1 and 2 and participates in cristae remodeling by the oligomerization of two L-OPA1 and one S-OPA1, which then interact with other protein complexes to alter cristae structure. Its cristae regulating function also contributes to its role in oxidative phosphorylation and apoptosis, as it is required to maintain mitochondrial activity during low-energy substrate availability. Moreover, stabilization of mitochondrial cristae by OPA1 protects against mitochondrial dysfunction, cytochrome c release, and reactive oxygen species production, thus preventing cell death. Mitochondrial SLC25A transporters can detect these low levels and stimulate OPA1 oligomerization, leading to tightening of the cristae, enhanced assembly of ATP synthase, and increased ATP production. Stress from an apoptotic response can interfere with OPA1 oligomerization and prevent mitochondrial fusion.