A model of UncI-assisted assembly of c11-ring. UncI binds to monomer (or some unassembled state of) c-subunit(s) in the membranes, assists their assembly into c11-ring, and leaves c11-ring as Na+ binds to c11-ring. Other subunits associate with c11-ring, and active F1Fo is formed. Without UncI, an inactive F1Fo complex is formed. In this complex, c-subunits are not assembled into c11-ring, and some fraction of a-subunit is lost. c′11 indicates an interim state of c11-ring formation.