title: Coupling of mitochondrial import and export translocases by receptor-mediated supercomplex formation.
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.
authors.affiliation: Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany.
authors.forename: Jian
authors.initials: J
authors.lastname: Qiu
authors.forename: Lena-Sophie
authors.initials: LS
authors.lastname: Wenz
authors.forename: Ralf M
authors.initials: RM
authors.lastname: Zerbes
authors.forename: Silke
authors.initials: S
authors.lastname: Oeljeklaus
authors.forename: Maria
authors.initials: M
authors.lastname: Bohnert
authors.forename: David A
authors.initials: DA
authors.lastname: Stroud
authors.forename: Christophe
authors.initials: C
authors.lastname: Wirth
authors.forename: Lars
authors.initials: L
authors.lastname: Ellenrieder
authors.forename: Nicolas
authors.initials: N
authors.lastname: Thornton
authors.forename: Stephan
authors.initials: S
authors.lastname: Kutik
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wiese
authors.forename: Agnes
authors.initials: A
authors.lastname: Schulze-Specking
authors.forename: Nicole
authors.initials: N
authors.lastname: Zufall
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Chacinska
authors.forename: Bernard
authors.initials: B
authors.lastname: Guiard
authors.forename: Carola
authors.initials: C
authors.lastname: Hunte
authors.forename: Bettina
authors.initials: B
authors.lastname: Warscheid
authors.forename: Martin
authors.initials: M
authors.lastname: van der Laan
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Pfanner
authors.forename: Nils
authors.initials: N
authors.lastname: Wiedemann
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
mesh_terms: D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation; D018272:Porins / Q000737:chemistry / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; C580894:Por1 protein, S cerevisiae; D018272:Porins; D029701:Saccharomyces cerevisiae Proteins; C487333:Sam50 protein, S cerevisiae; C090857:TOM22 protein, S cerevisiae; C066555:Tom40 protein, S cerevisiae