Mitofilin is an important organizer of mitochondrial architecture. The mitofilin sequence encodes a polypeptide with a central alpha-helical region with predicted coiled coil domains flanked by globular amino and carboxy termini. There are four isoforms of mitofilin, and 90/91 kDa mitofilin forms have been observed in western blots. Mitofilin is located in the inner mitochondrial membrane and interacts with several protein complexes of the outer membrane, thereby generating contact sites between the two membrane systems of mitochondria. These mitofilin-containing hetero-oligomeric protein complexes form the mitochondrial inner membrane organizing system (MINOS). MINOS integrity is required for the structural maintenance of the inner mitochondrial membrane. This mitochondrial region contains cristae membranes that form large tubular invaginations that protrude into the mitochondrial matrix. These cristae membranes contain the enzyme complexes of the oxidative phosphorylation machinery. MINOS deficiency causes loss of crista junction structures and the detachment of cristae from the inner boundary membrane.
