title: Genome-Wide Screens in Saccharomyces cerevisiae Highlight a Role for Cardiolipin in Biogenesis of Mitochondrial Outer Membrane Multispan Proteins.
abstract: A special group of mitochondrial outer membrane (MOM) proteins spans the membrane several times via multiple helical segments. Such multispan proteins are synthesized on cytosolic ribosomes before their targeting to mitochondria and insertion into the MOM. Previous work recognized the import receptor Tom70 and the mitochondrial import (MIM) complex, both residents of the MOM, as required for optimal biogenesis of these proteins. However, their involvement is not sufficient to explain either the entire import pathway or its regulation. To identify additional factors that are involved in the biogenesis of MOM multispan proteins, we performed complementary high-throughput visual and growth screens in Saccharomyces cerevisiae. Cardiolipin (CL) synthase (Crd1) appeared as a candidate in both screens. Our results indeed demonstrate lower steady-state levels of the multispan proteins Ugo1, Scm4, and Om14 in mitochondria from crd1Δ cells. Importantly, MOM single-span proteins were not affected by this mutation. Furthermore, organelles lacking Crd1 had a lower in vitro capacity to import newly synthesized Ugo1 and Scm4 molecules. Crd1, which is located in the mitochondrial inner membrane, condenses phosphatidylglycerol together with CDP-diacylglycerol to obtain de novo synthesized CL molecules. Hence, our findings suggest that CL is an important component in the biogenesis of MOM multispan proteins.
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tuebingen, Tuebingen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Sauerwald
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tuebingen, Tuebingen, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Jores
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Michal
authors.initials: M
authors.lastname: Eisenberg-Bord
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Silvia Gabriela
authors.initials: SG
authors.lastname: Chuartzman
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel maya.schuldiner@weizmann.ac.il doron.rapaport@uni-tuebingen.de.
authors.forename: Maya
authors.initials: M
authors.lastname: Schuldiner
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tuebingen, Tuebingen, Germany maya.schuldiner@weizmann.ac.il doron.rapaport@uni-tuebingen.de.
authors.forename: Doron
authors.initials: D
authors.lastname: Rapaport
mesh_terms: D002308:Cardiolipins / Q000096:biosynthesis*; D003567:Cytidine Diphosphate Diglycerides / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D049452:Green Fluorescent Proteins; D008565:Membrane Proteins / Q000096:biosynthesis / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000096:biosynthesis / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000096:biosynthesis; D010715:Phosphatidylglycerols / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis; D017855:Transferases (Other Substituted Phosphate Groups) / Q000378:metabolism*
chemical_list: D002308:Cardiolipins; D003567:Cytidine Diphosphate Diglycerides; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; C000600009:OM14 protein, S cerevisiae; D010715:Phosphatidylglycerols; C078718:SCM4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C423986:UGO1 protein, S cerevisiae; D049452:Green Fluorescent Proteins; D017855:Transferases (Other Substituted Phosphate Groups); C100091:cardiolipin synthetase