Binding to Chaperones Allows Import of a Purified Mitochondrial Precursor into Mitochondria

Artigues, Antonio; Iriarte, Ana; Martinez‐Carrion, Marino

doi:10.1074/jbc.m203474200

Cited by 24 publications

(23 citation statements)

References 57 publications

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“…In mitochondria several cytosolic factors have been proposed to influence the folding and protein import, and they are widely documented (46). Hsp70 molecular chaperones from cytosol and mitochondrial matrix interact with both presequences and mature parts of precursors (19,20,47,48). Standing evidences correlate the mitochondrial Hsp70s located in the matrix with the mitochondria protein import (49 -51).…”

Section: Discussionmentioning

confidence: 99%

Precursors with Altered Affinity for Hsp70 in Their Transit Peptides Are Efficiently Imported into Chloroplasts

Rial

Ottado

Ceccarelli

2003

Journal of Biological Chemistry

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Protein import into chloroplasts is postulated to occur with the involvement of molecular chaperones. We have determined that the transit peptide of ferredoxin-NADP(H) reductase precursor binds preferentially to an Hsp70 from chloroplast stroma. To investigate the role of Hsp70 molecular chaperones in chloroplast protein import, we analyzed the import into pea chloroplasts of preproteins with decreased Hsp70 binding affinity in their transit peptides. Our results indicate that the precursor with the lowest affinity for Hsp70 molecular chaperones in its transit peptide was imported to chloroplasts with similar apparent K m as the wild type precursor and a 2-fold increase in V max . Thus, a strong interaction between chloroplast stromal Hsp70 and the transit peptide seems not to be essential for protein import. These results indicate that in chloroplasts the main unfolding force during protein import may be applied by molecular chaperones other than Hsp70s. Although stromal Hsp70s undoubtedly participate in chloroplast biogenesis, the role of these molecular chaperones in chloroplast protein translocation differs from the one proposed in the mechanisms postulated up to date.

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Section: Discussionmentioning

confidence: 99%

Precursors with Altered Affinity for Hsp70 in Their Transit Peptides Are Efficiently Imported into Chloroplasts

Rial

Ottado

Ceccarelli

2003

Journal of Biological Chemistry

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“…There is also a report that the cytoplasmic Hsp70 chaperone binds mt precursor protein during translation in a cell-free extract (38) or by incubation with the purified precursor (39). Therefore, there is a possibility that the import inhibition of Mtf1p with 8 M urea pretreatment could be a secondary effect e.g.…”

Section: Fig 8 Import Of Urea-denatured Mtf1p or F 1 ␤ A Lanes 1 mentioning

confidence: 99%

Import of Yeast Mitochondrial Transcription Factor (Mtf1p) via a Nonconventional Pathway

Biswas¹,

Getz²

2002

Journal of Biological Chemistry

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The yeast mitochondrial (mt) transcription factor Mtf1p is imported into the mitochondria from the cytoplasm without a conventional mt-targeting presequence. To understand its import the mt translocation of wild type and mutant Mtf1p constructs was investigated in vitro under various assay conditions. We report here that Mtf1p, unlike most mt matrix proteins hitherto studied, is translocated into the mitochondria independent of membrane potential, ATP hydrolysis, and membrane receptor. This unusual import of Mtf1p was also observed on ice (3°C). Sub-mitochondrial fractionation demonstrated that Mtf1p was translocated in vitro to one or more of the same mt sites as the endogenous protein that includes the matrix. To identify the mt-targeting sequence of Mtf1p, various N-terminal, C-terminal, or internally deleted Mtf1p derivatives were generated. The full-length and C-terminal deletions but not the N-terminal truncated Mtf1p were imported into mitochondria, indicating the importance of its N-terminal sequence for mt targeting. However, the internal deletion of Mtf1p revealed that the first 150-amino acid N-terminal sequence alone was not sufficient for mt targeting of Mtf1p, suggesting that an extended rather than a short N-terminal sequence is required for import. We favor a model in which Mtf1p adopts an import-competent conformation during translation. Consistent with this model are three findings: most of the protein sequence appears to be required for optimal import, urea denaturation eliminates its import competence, and the import-competent form of the protein is more resistant to tryptic hydrolysis than is the denatured protein. This represents a novel mechanism for mitochondrial protein import.Mitochondria and chloroplasts are unique among eukaryotic organelles in possessing their own genomes. These extra-chromosomal DNAs are expressed by the organelle-specific transcription and translational machinery (1-5). The yeast mt 1 genome encodes seven protein subunits of the energy-transducing enzyme complexes imbedded in the inner membrane, one ribosomal protein (i.e. Var1) of the small mitoribosomal subunit, two rRNAs (i.e. 21 S and 15 S rRNAs for the large and small subunits, respectively), a complete set of tRNAs, and an

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“…For instance, E. coli DnaJ and its homologs participate in protein folding and the response to heat stress (Zuber et al, 1998). Yeast Ydj1p/Mas5p participates in protein translocation into the ER and mitochondria (McClellan and Brodsky, 2000;Artigues et al, 2002). Mammalian and yeast auxilins interact with their Hsc70 counterparts to disassemble clathrin triskelia from clathrin-coated vesicles during endocytosis (reviewed by Lemmon, 2001).…”

Section: Introductionmentioning

confidence: 99%

ALTERED RESPONSE TO GRAVITY Is a Peripheral Membrane Protein That Modulates Gravity-Induced Cytoplasmic Alkalinization and Lateral Auxin Transport in Plant Statocytes

et al. 2003

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ARG1 ( ALTERED RESPONSE TO GRAVITY ) is required for normal root and hypocotyl gravitropism. Here, we show that targeting ARG1 to the gravity-perceiving cells of roots or hypocotyls is sufficient to rescue the gravitropic defects in the corresponding organs of arg1-2 null mutants. The cytosolic alkalinization of root cap columella cells that normally occurs very rapidly upon gravistimulation is lacking in arg1-2 mutants. Additionally, vertically grown arg1-2 roots appear to accumulate a greater amount of auxin in an expanded domain of the root cap compared with the wild type, and no detectable lateral auxin gradient develops across mutant root caps in response to gravistimulation. We also demonstrate that ARG1 is a peripheral membrane protein that may share some subcellular compartments in the vesicular trafficking pathway with PIN auxin efflux carriers. These data support our hypothesis that ARG1 is involved early in gravitropic signal transduction within the gravity-perceiving cells, where it influences pH changes and auxin distribution. We propose that ARG1 affects the localization and/or activity of PIN or other proteins involved in lateral auxin transport.

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Binding to Chaperones Allows Import of a Purified Mitochondrial Precursor into Mitochondria

Cited by 24 publications

References 57 publications

Precursors with Altered Affinity for Hsp70 in Their Transit Peptides Are Efficiently Imported into Chloroplasts

Precursors with Altered Affinity for Hsp70 in Their Transit Peptides Are Efficiently Imported into Chloroplasts

Import of Yeast Mitochondrial Transcription Factor (Mtf1p) via a Nonconventional Pathway

ALTERED RESPONSE TO GRAVITY Is a Peripheral Membrane Protein That Modulates Gravity-Induced Cytoplasmic Alkalinization and Lateral Auxin Transport in Plant Statocytes

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