101
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Stanley WA, Fodor K, Marti-Renom MA, Schliebs W, Wilmanns M. Protein translocation into peroxisomes by ring-shaped import receptors. FEBS Lett 2007; 581:4795-802. [PMID: 17884042 DOI: 10.1016/j.febslet.2007.09.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Accepted: 09/04/2007] [Indexed: 12/27/2022]
Abstract
Folded and functional proteins destined for translocation from the cytosol into the peroxisomal matrix are recognized by two different peroxisomal import receptors, Pex5p and Pex7p. Both cargo-loaded receptors dock on the same translocon components, followed by cargo release and receptor recycling, as part of the complete translocation process. Recent structural and functional evidence on the Pex5p receptor has provided insight on the molecular requirements of specific cargo recognition, while the remaining processes still remain largely elusive. Comparison of experimental structures of Pex5p and a structural model of Pex7p reveal that both receptors are built by ring-like arrangements with cargo binding sites, central to the respective structures. Although, molecular insight into the complete peroxisomal translocon still remains to be determined, emerging data allow to deduce common molecular principles that may hold for other translocation systems as well.
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Affiliation(s)
- Will A Stanley
- ARC Plant Energy Biology Centre M316, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
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102
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Han D, Oh J, Kim K, Lim H, Kim Y. Crystal structure of YrrB: A TPR protein with an unusual peptide-binding site. Biochem Biophys Res Commun 2007; 360:784-90. [PMID: 17624311 DOI: 10.1016/j.bbrc.2007.06.129] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 06/22/2007] [Indexed: 11/29/2022]
Abstract
YrrB is a hypothetical protein containing a tetratricopeptide repeat (TPR) domain from a Gram-positive bacterium, Bacillus subtilis. We determined YrrB structure in the C2 space group to 2.5A resolution, which is the first TPR structure of the Gram-positive bacterium B. subtilis. In contrast to other known TPR structures, the concave surface of the YrrB TPR domain is composed of the putative peptide-binding pocket lined with positively-charged residues. This unique charge distribution reveals that YrrB can interact with partner proteins via an unusual TPR-mediated interaction mode, compared to that of other TPR-containing structures. Functional annotation using genomics analysis suggested that YrrB may be an interacting mediator in the complex formation among RNA sulfuration components. No proteins containing a TPR domain have been identified in the biosynthesis of sulfur-containing biomolecules. Thus, YrrB could play a new role as a connecting module among those proteins in the conserved gene cluster for RNA sulfuration.
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Affiliation(s)
- Dohyun Han
- College of Medicine, Seoul National University, Yongon-Dong, Seoul 110-799, Republic of Korea
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103
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Baker MJ, Frazier AE, Gulbis JM, Ryan MT. Mitochondrial protein-import machinery: correlating structure with function. Trends Cell Biol 2007; 17:456-64. [PMID: 17825565 DOI: 10.1016/j.tcb.2007.07.010] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Revised: 07/03/2007] [Accepted: 07/03/2007] [Indexed: 11/16/2022]
Abstract
Most mitochondrial proteins are synthesized in the cytosol, translocated into the organelle and directed along specific sorting pathways. Over the past 20 years, >30 proteins have been identified as having key roles in mitochondrial protein import. Recently, the elucidation of the structures of several import components has provided fresh insight into the import process. Here, we review the different pathways involved in sorting proteins into mitochondrial subcompartments. Along the way, we highlight the available structural information about the protein-import machinery and discuss how these structures correlate with previously ascribed functions. Future challenges for the cell biologists will be to use this structural information to test specific hypotheses addressing the molecular mechanisms of mitochondrial protein import.
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Affiliation(s)
- Michael J Baker
- Department of Biochemistry, La Trobe University, Melbourne 3086, Australia
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104
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Bhangoo MK, Tzankov S, Fan AC, Dejgaard K, Thomas DY, Young JC. Multiple 40-kDa heat-shock protein chaperones function in Tom70-dependent mitochondrial import. Mol Biol Cell 2007; 18:3414-28. [PMID: 17596514 PMCID: PMC1951752 DOI: 10.1091/mbc.e07-01-0088] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mitochondrial preproteins that are imported via the translocase of the mitochondrial outer membrane (Tom)70 receptor are complexed with cytosolic chaperones before targeting to the mitochondrial outer membrane. The adenine nucleotide transporter (ANT) follows this pathway, and its purified mature form is identical to the preprotein. Purified ANT was reconstituted with chaperones in reticulocyte lysate, and bound proteins were identified by mass spectrometry. In addition to 70-kDa heat-shock cognate protein (Hsc70) and 90-kDa heat-shock protein (Hsp90), a specific subset of cochaperones were found, but no mitochondria-specific targeting factors were found. Interestingly, three different Hsp40-related J-domain proteins were identified: DJA1, DJA2, and DJA4. The DJAs bound preproteins to different extents through their C-terminal regions. DJA dominant-negative mutants lacking the N-terminal J-domains impaired mitochondrial import. The mutants blocked the binding of Hsc70 to preprotein, but with varying efficiency. The DJAs also showed significant differences in activation of the Hsc70 ATPase and Hsc70-dependent protein refolding. In HeLa cells, the DJAs increased new protein folding and mitochondrial import, although to different extents. No single DJA was superior to the others in all aspects, but each had a profile of partial specialization. The Hsp90 cochaperones p23 and Aha1 also regulated Hsp90-preprotein interactions. We suggest that multiple cochaperones with similar yet partially specialized properties cooperate in optimal chaperone-preprotein complexes.
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Affiliation(s)
- Melanie K. Bhangoo
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Stefan Tzankov
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Anna C.Y. Fan
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Kurt Dejgaard
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - David Y. Thomas
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Jason C. Young
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
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105
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Current awareness on yeast. Yeast 2007. [DOI: 10.1002/yea.1323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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106
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Albrecht R, Rehling P, Chacinska A, Brix J, Cadamuro SA, Volkmer R, Guiard B, Pfanner N, Zeth K. The Tim21 binding domain connects the preprotein translocases of both mitochondrial membranes. EMBO Rep 2006; 7:1233-8. [PMID: 17099692 PMCID: PMC1794701 DOI: 10.1038/sj.embor.7400828] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Revised: 08/11/2006] [Accepted: 09/08/2006] [Indexed: 11/08/2022] Open
Abstract
Proteins destined for the mitochondrial matrix are imported by the translocase of the outer membrane--the TOM complex--and the presequence translocase of the inner membrane--the TIM23 complex. At present, there is no structural information on components of the presequence translocase. Tim21, a subunit of the presequence translocase consisting of a membrane anchor and a carboxy-terminal domain exposed to the intermembrane space, directly connects the TOM and TIM23 complexes by binding to the intermembrane space domain of the Tom22 receptor. We crystallized the binding domain of Tim21 of Saccharomyces cerevisiae and determined its structure at 1.6 A resolution. The Tim21 structure represents a new alpha/beta-mixed protein fold with two alpha-helices flanked by an extended eight-stranded beta-sheet. We also identified a core sequence of Tom22 that binds to Tim21. Furthermore, negatively charged amino-acid residues of Tom22 are important for binding to Tim21. Here we suggest a mechanism for the TOM-TIM interaction.
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Affiliation(s)
- Reinhard Albrecht
- Max-Planck-Institut für Biochemie, Abteilung Membranbiochemie, Am Klopferspitz 18, D-82512 Martinsried, Germany
- Max-Planck-Institut für Entwicklungsbiologie, Abteilung Protein Evolution, Spemannstraße 35/I, D-72076 Tübingen, Germany
| | - Peter Rehling
- Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, Hermann-Herder-Straße 7, D-79104 Freiburg, Germany
| | - Agnieszka Chacinska
- Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, Hermann-Herder-Straße 7, D-79104 Freiburg, Germany
| | - Jan Brix
- Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, Hermann-Herder-Straße 7, D-79104 Freiburg, Germany
| | - Sergio A Cadamuro
- Max-Planck-Institut für Biochemie, Laboratory of Bioorganic Chemistry, Am Klopferspitz 18, D-82512 Martinsried, Germany
| | - Rudolf Volkmer
- Institut für Medizinische Immunologie, Charité—Universitätsmedizin Berlin, Hessische Straße 3–4, D-10115 Berlin, Germany
| | - Bernard Guiard
- Centre de Génétique Moléculaire, CNRS, Avenue de la Terrasse—Bât. 26, F-91190 Gif-sur-Yvette, France
| | - Nikolaus Pfanner
- Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, Hermann-Herder-Straße 7, D-79104 Freiburg, Germany
- Tel: +49 761 2035224; Fax: +49 761 2035261; E-mail:
| | - Kornelius Zeth
- Max-Planck-Institut für Biochemie, Abteilung Membranbiochemie, Am Klopferspitz 18, D-82512 Martinsried, Germany
- Max-Planck-Institut für Entwicklungsbiologie, Abteilung Protein Evolution, Spemannstraße 35/I, D-72076 Tübingen, Germany
- Tel: +49 7071 601 323; Fax: +49 7071 601 349; E-mail:
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107
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Chou CH, Lee RS, Yang-Yen HF. An internal EELD domain facilitates mitochondrial targeting of Mcl-1 via a Tom70-dependent pathway. Mol Biol Cell 2006; 17:3952-63. [PMID: 16822835 PMCID: PMC1593170 DOI: 10.1091/mbc.e06-04-0319] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mcl-1 functions at an apical step in many regulatory programs that control cell death. Although the mitochondrion is one major subcellular organelle where Mcl-1 functions, the molecular mechanism by which Mcl-1 is targeted to mitochondria remains unclear. Here, we demonstrate that Mcl-1 is loosely associated with the outer membrane of mitochondria. Furthermore, we demonstrate that Mcl-1 interacts with the mitochondrial import receptor Tom70, and such interaction requires an internal domain of Mcl-1 that contains an EELD motif. A Tom70 antibody that blocks Mcl-1-Tom70 interaction blocks mitochondrial import of Mcl-1 in vitro. Furthermore, Mcl-1 is significantly less targeted to mitochondria in Tom70 knockdown than in the control cells. Similar targeting preference is also observed for the DM mutant of Mcl-1 whose mutation at the EELD motif markedly attenuates its Tom70 binding activity. Together, our results indicate that the internal EELD domain facilitates mitochondrial targeting of Mcl-1 via a Tom70-dependent pathway.
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Affiliation(s)
- Chiang-Hung Chou
- *Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 114, Taiwan
| | - Ru-Shuo Lee
- Graduate Institute of Cell and Molecular Biology, Taipei Medical University, Taipei 110, Taiwan; and
| | - Hsin-Fang Yang-Yen
- *Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 114, Taiwan
- Graduate Institute of Cell and Molecular Biology, Taipei Medical University, Taipei 110, Taiwan; and
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
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