title: Ribosome-Associated Mba1 Escorts Cox2 from Insertion Machinery to Maturing Assembly Intermediates.
abstract: The three conserved core subunits of the cytochromecoxidase are encoded by mitochondria in close to all eukaryotes. The Cox2 subunit spans the inner membrane twice, exposing the N and C termini to the intermembrane space. For this, the N terminus is exported cotranslationally by Oxa1 and subsequently undergoes proteolytic maturation inSaccharomyces cerevisiaeLittle is known about the translocation of the C terminus, but Cox18 has been identified to be a critical protein in this process. Here we find that the scaffold protein Cox20, which promotes processing of Cox2, is in complex with the ribosome receptor Mba1 and translating mitochondrial ribosomes in a Cox2-dependent manner. The Mba1-Cox20 complex accumulates when export of the C terminus of Cox2 is blocked by the loss of the Cox18 protein. While Cox20 engages with Cox18, Mba1 is no longer present at this stage. Our analyses indicate that Cox20 associates with nascent Cox2 and Mba1 to promote Cox2 maturation cotranslationally. We suggest that Mba1 stabilizes the Cox20-ribosome complex and supports the handover of Cox2 to the Cox18 tail export machinery.
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, GZMB, Göttingen, Germany.
authors.forename: Isotta
authors.initials: I
authors.lastname: Lorenzi
authors.affiliation: Faculty of Biology, Department of Biochemistry and Functional Proteomics, University of Freiburg, Freiburg, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Oeljeklaus
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, GZMB, Göttingen, Germany.
authors.forename: Christin
authors.initials: C
authors.lastname: Ronsör
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, GZMB, Göttingen, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Bareth
authors.affiliation: Faculty of Biology, Department of Biochemistry and Functional Proteomics, University of Freiburg, Freiburg, Germany.|BIOSS Center for Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Warscheid
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, GZMB, Göttingen, Germany Peter.Rehling@medizin.uni-goettingen.de.|Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Rehling
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, GZMB, Göttingen, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Dennerlein