title: Phosphatidylcholine affects the role of the sorting and assembly machinery in the biogenesis of mitochondrial β-barrel proteins.
abstract: Two protein translocases drive the import of β-barrel precursor proteins into the mitochondrial outer membrane: The translocase of the outer membrane (TOM complex) promotes transport of the precursor to the intermembrane space, whereas the sorting and assembly machinery (SAM complex) mediates subsequent folding of the β-barrel and its integration into the target membrane. The non-bilayer-forming phospholipids phosphatidylethanolamine (PE) and cardiolipin (CL) are required for the biogenesis of β-barrel proteins. Whether bilayer-forming phospholipids such as phosphatidylcholine (PC), the most abundant phospholipid of the mitochondrial outer membrane, play a role in the import of β-barrel precursors is unclear. In this study, we show that PC is required for stability and function of the SAM complex during the biogenesis of β-barrel proteins. PC further promotes the SAM-dependent assembly of the TOM complex, indicating a general role of PC for the function of the SAM complex. In contrast to PE-deficient mitochondria precursor accumulation at the TOM complex is not affected by depletion of PC. We conclude that PC and PE affect the function of distinct protein translocases in mitochondrial β-barrel biogenesis.
authors.affiliation: From the Institute for Biochemistry and Molecular Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Max-Hinderk
authors.initials: MH
authors.lastname: Schuler
authors.affiliation: Institute for Biochemistry, Graz University of Technology, NaWi Graz, A-8010 Graz, Austria.
authors.forename: Francesca
authors.initials: F
authors.lastname: Di Bartolomeo
authors.affiliation: From the Institute for Biochemistry and Molecular Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Böttinger
authors.affiliation: From the Institute for Biochemistry and Molecular Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Susanne E
authors.initials: SE
authors.lastname: Horvath
authors.affiliation: From the Institute for Biochemistry and Molecular Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Lena-Sophie
authors.initials: LS
authors.lastname: Wenz
authors.affiliation: Institute for Biochemistry, Graz University of Technology, NaWi Graz, A-8010 Graz, Austria, guenther.daum@tugraz.at.
authors.forename: Günther
authors.initials: G
authors.lastname: Daum
authors.affiliation: From the Institute for Biochemistry and Molecular Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany, BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany thomas.becker@biochemie.uni-freiburg.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
mesh_terms: D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D024101:Mitochondrial Proteins; D010713:Phosphatidylcholines; D029701:Saccharomyces cerevisiae Proteins
keywords: SAM complex; TOM complex; mitochondria; phosphatidylcholine; phosphatidylethanolamine; protein complex; protein sorting; protein translocation