P10 - Structural basis and organization of human cytochrome c oxidase biogenesis

Mitochondria are sub-cellular organelles that produce ATP by oxidative phosphorylation. This is carried out by the respiratory chain and ATP synthase, a series of multi-subunit protein complexes embedded in the inner mitochondrial membrane. The biogenesis of these complexes requires the coordinated assembly of subunits encoded in the nuclear genome and subunits expressed from the mitochondrial genome. Although many human mitochondrial diseases are caused by defects in respiratory chain assembly, this process remains poorly understood. In particular, it is not known how the assembly of the imported subunits and the mitochondrially-encoded subunits is functionally, temporally and spatially coordinated. In this project, we will determine the molecular basis and organization of complex IV biogenesis in human mitochondria. In particular, we will use single-particle cryo-electron microscopy to determine the structure and composition of an early complex IV biogenesis intermediate, which can be isolated via the mitochondrial inner membrane insertase OXA1L. This complex contains the mitochondria-encoded subunit COX2, a number of assembly factors involved in cofactor insertion, as well as the mitochondrial ribosome, suggesting that it represents a co-translational assembly intermediate. Furthermore, we will employ the pipeline for cryo-electron tomography of human mitochondria which we have established with the help of the FOR2848 startup module funding to define the structure and organization of mitochondrial ribosome-associated complexes in situ. Together, this will provide molecular insights into the mechanism of cytochrome c oxidase biogenesis, how this process is functionally coupled to mitochondrial translation and how respiratory chain biogenesis is spatially organized at the inner mitochondrial membrane.