Abstract
Eukaryotic AAA proteases form a conserved family of membrane-embedded ATP-dependent proteases but have been analyzed functionally only in the yeast Saccharomyces cerevisiae. Here, we have identified two novel members of this protein family in the filamentous fungus Neurospora crassa, which were termed MAP-1 and IAP-1. Both proteins are localized to the inner membrane of mitochondria. They are part of two similar-sized high molecular mass complexes, but expose their catalytic sites to opposite membrane surfaces, namely, the intermembrane and the matrix space. Disruption of iap-1 by repeat-induced point mutation caused a slow growth phenotype at high temperature and stabilization of a misfolded inner membrane protein against degradation. IAP-1 could partially substitute for functions of its yeast homolog Yme1, demonstrating functional conservation. However, respiratory growth at 37 degrees C was not restored. Our results identify two components of the quality control system of the mitochondrial inner membrane in N. crassa and suggest that AAA proteases with catalytic sites exposed to opposite membrane surfaces are present in mitochondria of all eukaryotic cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP-Dependent Proteases
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism
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Amino Acid Sequence
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Catalytic Domain
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Chromatography, Gel
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Cloning, Molecular
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Fungal Proteins / chemistry
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Fungal Proteins / genetics
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Fungal Proteins / metabolism
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Genes, Fungal / genetics
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Genetic Complementation Test
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Intracellular Membranes / enzymology*
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Intracellular Membranes / metabolism
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Macromolecular Substances
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Membrane Proteins / chemistry
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Metalloendopeptidases / chemistry*
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Metalloendopeptidases / genetics
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Metalloendopeptidases / metabolism*
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Mitochondria / enzymology*
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Molecular Sequence Data
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Molecular Weight
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Mutation
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Neurospora crassa / cytology
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Neurospora crassa / enzymology*
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Protein Folding
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Protein Subunits
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism
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Sequence Homology, Amino Acid
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Temperature
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Time Factors
Substances
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Fungal Proteins
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Macromolecular Substances
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Membrane Proteins
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Protein Subunits
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Saccharomyces cerevisiae Proteins
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ATP-Dependent Proteases
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YME1 protein, S cerevisiae
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Metalloendopeptidases
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intermembrane space AAA protease-1
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m-AAA proteases
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matrix AAA protease-1
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Adenosine Triphosphatases