title: Mitochondrial inner membrane protease promotes assembly of presequence translocase by removing a carboxy-terminal targeting sequence.
abstract: The presequence translocase of the inner mitochondrial membrane (TIM23 complex) is essential for importing cleavable preproteins into mitochondria. The preproteins contain amino-terminal targeting sequences that are removed by the mitochondrial processing peptidase (MPP). Some preproteins carry bipartite presequences that are cleaved twice, by MPP and the inner membrane protease (IMP). Here, we report that the TIM23 complex is altered in mitochondria lacking the IMP subunit Imp1 although none of the TIM23 components contains a bipartite presequence. We show that the TIM23 subunit Mgr2 is processed by IMP, but not by MPP. The cytosolic precursor of Mgr2 contains a carboxy-terminal sequence that promotes targeting to mitochondria, but impairs stable assembly and function of the mature TIM23 complex. IMP removes the carboxy-terminal targeting sequence and thus promotes proper assembly of the TIM23 complex. Our results reveal carboxy-terminal processing as a new mechanism in the biogenesis of the mitochondrial inner membrane.
authors.affiliation: Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Ieva
authors.forename: Anna K
authors.initials: AK
authors.lastname: Heißwolf
authors.forename: Michael
authors.initials: M
authors.lastname: Gebert
authors.forename: F-Nora
authors.initials: FN
authors.lastname: Vögtle
authors.forename: Florian
authors.initials: F
authors.lastname: Wollweber
authors.forename: Carola S
authors.initials: CS
authors.lastname: Mehnert
authors.forename: Silke
authors.initials: S
authors.lastname: Oeljeklaus
authors.forename: Bettina
authors.initials: B
authors.lastname: Warscheid
authors.forename: Chris
authors.initials: C
authors.lastname: Meisinger
authors.forename: Martin
authors.initials: M
authors.lastname: van der Laan
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Pfanner
mesh_terms: D020816:Amino Acid Motifs; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000737:chemistry / Q000378:metabolism; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C574457:Mgr2 protein, S cerevisiae; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; C083081:TIM23 protein, S cerevisiae; D010450:Endopeptidases; C067167:IMP1 protein, S cerevisiae