title: The role of Djp1 in import of the mitochondrial protein Mim1 demonstrates specificity between a cochaperone and its substrate protein.
abstract: A special group of mitochondrial outer membrane proteins spans the membrane once, exposing soluble domains to both sides of the membrane. These proteins are synthesized in the cytosol and then inserted into the membrane by an unknown mechanism. To identify proteins that are involved in the biogenesis of the single-span model protein Mim1, we performed a high-throughput screen in yeast. Two interesting candidates were the cytosolic cochaperone Djp1 and the mitochondrial import receptor Tom70. Our results indeed demonstrate a direct interaction of newly synthesized Mim1 molecules with Tom70. We further observed lower steady-state levels of Mim1 in mitochondria from djp1Δ and tom70 tom71Δ cells and massive mislocalization of overexpressed GFP-Mim1 to the endoplasmic reticulum in the absence of Djp1. Importantly, these phenotypes were observed specifically for the deletion of DJP1 and were not detected in mutant cells lacking any of the other cytosolic cochaperones of the Hsp40 family. Furthermore, the djp1Δ tom70Δ tom71Δ triple deletion resulted in a severe synthetic sick/lethal growth phenotype. Taking our results together, we identified Tom70 and Djp1 as crucial players in the biogenesis of Mim1. Moreover, the involvement of Djp1 provides a unique case of specificity between a cochaperone and its substrate protein.
authors: Interfaculty Institute of Biochemistry, University of Tuebingen, Tuebingen, Germany.
authors: Dražen
authors: D
authors: Papić
authors: Yael
authors: Y
authors: Elbaz-Alon
authors: Sophia Nina
authors: SN
authors: Koerdt
authors: Karoline
authors: K
authors: Leopold
authors: Dennis
authors: D
authors: Worm
authors: Martin
authors: M
authors: Jung
authors: Maya
authors: M
authors: Schuldiner
authors: Doron
authors: D
authors: Rapaport
mesh_terms: D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000172:deficiency / Q000235:genetics*; D051336:Mitochondrial Membranes / Q000378:metabolism; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D018832:Molecular Chaperones / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: C584545:Djp1 protein, S cerevisiae; C492709:MIM1 protein, S cerevisiae; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; C489039:TOM70 protein, S cerevisiae; C099144:TOM71 protein, S cerevisiae; D049452:Green Fluorescent Proteins
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