title: Composition and topology of the endoplasmic reticulum-mitochondria encounter structure.
abstract: Eukaryotic cells contain multiple organelles, which are functionally and structurally interconnected. The endoplasmic reticulum-mitochondria encounter structure (ERMES) forms a junction between mitochondria and the endoplasmic reticulum (ER). Four ERMES proteins are known in yeast, the ER-anchored protein Mmm1 and three mitochondria-associated proteins, Mdm10, Mdm12 and Mdm34, with functions related to mitochondrial morphology and protein biogenesis. We mapped the glycosylation sites of ERMES and demonstrate that three asparagine residues in the N‑terminal domain of Mmm1 are glycosylated. While the glycosylation is dispensable, the cytosolic C‑terminal domain of Mmm1 that connects to the Mdm proteins is required for Mmm1 function. To analyze the composition of ERMES, we determined the subunits by quantitative mass spectrometry. We identified the calcium-binding GTPase Gem1 as a new ERMES subunit, revealing that ERMES is composed of five genuine subunits. Taken together, ERMES represents a platform that integrates components with functions in formation of ER-mitochondria junctions, maintenance of mitochondrial morphology, protein biogenesis and calcium binding.
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: Silke
authors.initials: S
authors.lastname: Oeljeklaus
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wiese
authors.forename: Maria
authors.initials: M
authors.lastname: Bohnert
authors.forename: Urs
authors.initials: U
authors.lastname: Lewandrowski
authors.forename: Albert
authors.initials: A
authors.lastname: Sickmann
authors.forename: Bernard
authors.initials: B
authors.lastname: Guiard
authors.forename: Martin
authors.initials: M
authors.lastname: van der Laan
authors.forename: Bettina
authors.initials: B
authors.lastname: Warscheid
authors.forename: Nils
authors.initials: N
authors.lastname: Wiedemann
mesh_terms: D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*; D006031:Glycosylation; D013058:Mass Spectrometry; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008956:Models, Chemical; D025941:Protein Interaction Mapping; D055503:Protein Multimerization; D021122:Protein Subunits / Q000032:analysis; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins