Fig. 4: Mitochondrial fusion of the outer membrane is driven by mitofusin 1 and 2 (MfN 1/2), while the inner membrane requires a healthy balance of optic atrophy 1 (Opa1) isoforms.

Cleaved by Oma1, Opa1 produces short and long isoforms, both of which support fusion. Membrane bound long - Opa1 interacts with cardiolipin on the opposing membrane in a GTPase dependent manner and promotes lipid fusion of the inner membrane.