Participation of NDUFAF5 in the pathway of assembly of human complex I. Assembly factors associated stably with sub-complexes in the pathway are indicated. Hydroxylation of NDUFS7 by NDUFAF5 occurs at an early stage. The scheme is derived from an earlier version (19), and it is not known whether the 200-kDa sub-complex is associated with the membrane or not, as indicated. The 200-kDa sub-complex joins with membrane subunit ND1 and assembly factor C3orf1, plus subunits NDUFA3, NDUFA8, and NDUFA13 to form the 315-kDa membrane-bound sub-complex (13).