| dc.description.abstracteng | The catalytic core of the cytochrome c oxidase (complex IV), the terminal
enzyme of the mitochondrial respiratory chain, comprises three
mitochondria-encoded subunits Cox1, Cox2 and Cox3 that are highly
conserved among species. Cytochrome c oxidase maturation is a coordinated
process requiring specialized assembly factors that assist in the sequential
formation of sub-complexes, also termed assembly intermediates.
In recent decades, fruitful research of complex IV biogenesis, in the yeast S.
cerevisiae, has revealed that Cox2 is inserted into the inner mitochondrial
membrane via a co-translational mechanism. This is facilitated by the
mitochondrial ribosome binding protein Mba1 and the Oxa1 insertase.
Following insertion, various assembly factors, such as Cox20, are required for
the maturation of Cox2. However, the mechanism by which insertion and
assembly are coordinated is not well understood.
The Cox20 protein is a ubiquitous Cox2-chaperone, involved in Cox2 Nterminal
processing. In human, Cox2 is expressed without N-terminal
peptide, suggesting an additional role of Cox20 beyond its processing
function. In fact, a patient mutation in the Cox20 human homolog leads to
impaired cytochrome c oxidase assembly.
Results presented in this thesis elucidate the molecular role of Cox20 in the
early steps of Cox2 biogenesis. For this purpose, a mass spectrometry analysis
using a SILAC approach was undertaken to identify novel Cox20 interacting
partners. Analysis of the composition of Cox20-containing complexes
revealed proteins involved in Cox2 translation, membrane insertion and
metallation.
For the first time, the identified interaction with the mitochondrial ribosome
provides a new link of Cox20 function to Cox2 synthesis. Furthermore,
functional analysis of the novel Cox20-Mba1 complex suggested a novel role
of Mba1 with regard to Cox2 maturation. The presented data propose a new
shuttling mechanism of newly translated Cox2 from the ribosome and the
insertion machinery to maturing mitochondrial assembly intermediates. | de |