FIG. 1.

Mitochondrial fusion. Outer mitochondrial membrane fusion requires mitofusins located on the outer mitochondrial membrane by two transmembrane domains that tether adjacent mitochondria together by oligomerization of Mfn molecules located on opposing organelles. Fusion of the outer mitochondrial membranes requires GTPase activity. Following outer membrane fusion, OPA1, an intermembrane protein, mediates fusion of the inner mitochondrial membrane, which requires oligomerization of OPA1 and GTPase activity.