Author/Authors :
Jian Qiu ، نويسنده , , Lena-Sophie Wenz، نويسنده , , Ralf M. Zerbes، نويسنده , , Silke Oeljeklaus، نويسنده , , Maria Bohnert، نويسنده , , David A. Stroud، نويسنده , , Christophe Wirth، نويسنده , , Lars Ellenrieder، نويسنده , , Nicolas Thornton، نويسنده , , Stephan Kutik، نويسنده , , Sebastian Wiese، نويسنده , , Agnes Schulze-Specking، نويسنده , , Nicole Zufall، نويسنده , , Agnieszka Chacinska، نويسنده , , Bernard Guiard، نويسنده , , Carola Hunte، نويسنده , , Bettina Warscheid، نويسنده , , Martin van der Laan، نويسنده , , Nikolaus Pfanner، نويسنده , , Nils Wiedemann، نويسنده , , et al، نويسنده ,
Abstract :
The mitochondrial outer membrane harbors two protein translocases that are essential for cell viability: the translocase of the outer mitochondrial membrane (TOM) and the sorting and assembly machinery (SAM). The precursors of β-barrel proteins use both translocases—TOM for import to the intermembrane space and SAM for export into the outer membrane. It is unknown if the translocases cooperate and where the β-barrel of newly imported proteins is formed. We established a position-specific assay for monitoring β-barrel formation in vivo and in organello and demonstrated that the β-barrel was formed and membrane inserted while the precursor was bound to SAM. β-barrel formation was inhibited by SAM mutants and, unexpectedly, by mutants of the central import receptor, Tom22. We show that the cytosolic domain of Tom22 links TOM and SAM into a supercomplex, facilitating precursor transfer on the intermembrane space side. Our study reveals receptor-mediated coupling of import and export translocases as a means of precursor channeling.
