Scaffold protein that participates in the c-ring assembly of mitochondrial ATP synthase (F(1)F(0) ATP synthase or complex V) by facilitating the membrane insertion and oligomer formation of the subunit c/ATP5MC3. Participates in the incorporation of the c-ring into vestigial complexes. Additionally influences the incorporation of subunits MT-ATP6, MT-ATP8, ATP5MJ, and ATP5MK in the ATP synthase. Belongs to the TMEM242 family.