title: Biogenesis of mitochondrial β-barrel proteins: the POTRA domain is involved in precursor release from the SAM complex.
abstract: The mitochondrial outer membrane contains proteinaceous machineries for the translocation of precursor proteins. The sorting and assembly machinery (SAM) is required for the insertion of β-barrel proteins into the outer membrane. Sam50 is the channel-forming core subunit of the SAM complex and belongs to the BamA/Sam50/Toc75 family of proteins that have been conserved from Gram-negative bacteria to mitochondria and chloroplasts. These proteins contain one or more N-terminal polypeptide transport-associated (POTRA) domains. POTRA domains can bind precursor proteins, however, different views exist on the role of POTRA domains in the biogenesis of β-barrel proteins. It has been suggested that the single POTRA domain of mitochondrial Sam50 plays a receptor-like function at the SAM complex. We established a system to monitor the interaction of chemical amounts of β-barrel precursor proteins with the SAM complex of wild-type and mutant yeast in organello. We report that the SAM complex lacking the POTRA domain of Sam50 efficiently binds β-barrel precursors, but is impaired in the release of the precursors. These results indicate the POTRA domain of Sam50 is not essential for recognition of β-barrel precursors but functions in a subsequent step to promote the release of precursor proteins from the SAM complex.
authors.affiliation: Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany.
authors.forename: David A
authors.initials: DA
authors.lastname: Stroud
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
authors.forename: Jian
authors.initials: J
authors.lastname: Qiu
authors.forename: Diana
authors.initials: D
authors.lastname: Stojanovski
authors.forename: Sylvia
authors.initials: S
authors.lastname: Pfannschmidt
authors.forename: Christophe
authors.initials: C
authors.lastname: Wirth
authors.forename: Carola
authors.initials: C
authors.lastname: Hunte
authors.forename: Bernard
authors.initials: B
authors.lastname: Guiard
authors.forename: Chris
authors.initials: C
authors.lastname: Meisinger
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Pfanner
authors.forename: Nils
authors.initials: N
authors.lastname: Wiedemann
mesh_terms: D002474:Cell-Free System; D055786:Gene Knockout Techniques; D008928:Mitochondria / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D018272:Porins / Q000737:chemistry / Q000378:metabolism; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes; D050505:Mutant Proteins; D018272:Porins; D011498:Protein Precursors; D021382:Protein Sorting Signals; D029701:Saccharomyces cerevisiae Proteins; C487333:Sam50 protein, S cerevisiae