Insights into complex I assembly: Function of NDUFAF1 and a link with cardiolipin remodeling

Respiratory complex I is a similar to 1-MDa proton pump in mitochondria. Its structure has been revealed in great detail, but the structural basis of its assembly, in humans involving at least 15 assembly factors, is essentially unknown. We determined cryo-electron microscopy structures of assembly intermediates associated with assembly factor NDUFAF1 in a yeast model system. Subunits ND2 and NDUFC2 together with assembly factors NDUFAF1 and CIA84 form the nucleation point of the NDUFAF1-dependent assembly pathway. Unexpectedly, the cardiolipin remodeling enzyme tafazzin is an integral component of this core complex. In a later intermediate, all 12 subunits of the proximal proton pump module have assembled. NDUFAF1 locks the central ND3 subunit in an assembly-competent conformation, and major rearrangements of central subunits are required for complex I maturation.

Automated summary

Cryo-electron microscopy was used to determine the structure of assembly intermediates associated with NDUFAF1. It was found that NDUFAF1, together with ND2, NDUFC2, and CIA84, forms the nucleation point of the assembly pathway. The central subunit ND3 is locked in an assembly-competent conformation by NDUFAF1, and major rearrangements of central subunits are required for complex I maturation.