Ribosome binding to the Oxa1 complex facilitates co-translational protein insertion in mitochondria.
The Oxa1 translocase of the mitochondrial inner membrane facilitates the insertion of both mitochondrially and nuclear-encoded proteins from the matrix into the inner membrane. Most mitochondrially encoded proteins are hydrophobic membrane proteins which are integrated into the lipid bilayer during their synthesis on mitochondrial ribosomes. The molecular mechanism of this co-translational insertion process is unknown. Here we show that the matrix-exposed C-terminus of Oxa1 forms an alpha-helical domain that has the ability to bind to mitochondrial ribosomes. Deletion of this Oxa1 domain strongly diminished the efficiency of membrane insertion of subunit 2 of cytochrome oxidase, a mitochondrially encoded substrate of the Oxa1 translocase. This suggests that co-translational membrane insertion of mitochondrial translation products is facilitated by a physical interaction of translation complexes with the membrane-bound translocase.
Szyrach
Gregor
G
Institut für Physiologische Chemie, Butenandtstrasse 5, D-81377 München, Germany.
Ott
Martin
M
Bonnefoy
Nathalie
N
Neupert
Walter
W
Herrmann
Johannes M
JM
D002846:Chromatography, Affinity; D003576:Electron Transport Complex IV; D005982:Glutathione Transferase / Q000378:metabolism; D007425:Intracellular Membranes / Q000502:physiology; D008928:Mitochondria / Q000502:physiology*; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010101:Oxygen Consumption; D014176:Protein Biosynthesis; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D012269:Ribosomal Proteins / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C090858:OXA1 protein; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D003576:Electron Transport Complex IV; D005982:Glutathione Transferase