Structural domains comprising this superfamily share the structure of the mitochondrial ATP synthase-coupling factor 6, also known as subunit 6, of the the F0 complex of ATP synthases in mitochondria. The F6 subunit is part of the peripheral stalk that links the F1 and F0 complexes together, and which acts as a stator to prevent certain subunits from rotating with the central rotary element. The peripheral stalk differs in subunit composition between mitochondrial, chloroplast and bacterial ATPases. In mitochondria, the peripheral stalk is composed of one copy each of subunits OSCP (oligomycin sensitivity conferral protein), F6, B and D PMID:16045926. No homologue of subunit F6 can be found in bacterial or chloroplast ATP synthases, as their peripheral stalks are composed of one copy of the delta subunit (homologous to OSCP), and two copies of subunit B in bacteria, or one copy each of subunits B and B' in chloroplasts and photosynthetic bacteria (INTERPRO:IPR008387).