1
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Carmichael RE, Schrader M. Determinants of Peroxisome Membrane Dynamics. Front Physiol 2022; 13:834411. [PMID: 35185625 PMCID: PMC8853631 DOI: 10.3389/fphys.2022.834411] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 01/12/2022] [Indexed: 11/13/2022] Open
Abstract
Organelles within the cell are highly dynamic entities, requiring dramatic morphological changes to support their function and maintenance. As a result, organelle membranes are also highly dynamic, adapting to a range of topologies as the organelle changes shape. In particular, peroxisomes—small, ubiquitous organelles involved in lipid metabolism and reactive oxygen species homeostasis—display a striking plasticity, for example, during the growth and division process by which they proliferate. During this process, the membrane of an existing peroxisome elongates to form a tubule, which then constricts and ultimately undergoes scission to generate new peroxisomes. Dysfunction of this plasticity leads to diseases with developmental and neurological phenotypes, highlighting the importance of peroxisome dynamics for healthy cell function. What controls the dynamics of peroxisomal membranes, and how this influences the dynamics of the peroxisomes themselves, is just beginning to be understood. In this review, we consider how the composition, biophysical properties, and protein-lipid interactions of peroxisomal membranes impacts on their dynamics, and in turn on the biogenesis and function of peroxisomes. In particular, we focus on the effect of the peroxin PEX11 on the peroxisome membrane, and its function as a major regulator of growth and division. Understanding the roles and regulation of peroxisomal membrane dynamics necessitates a multidisciplinary approach, encompassing knowledge across a range of model species and a number of fields including lipid biochemistry, biophysics and computational biology. Here, we present an integrated overview of our current understanding of the determinants of peroxisome membrane dynamics, and reflect on the outstanding questions still remaining to be solved.
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Affiliation(s)
- Ruth E Carmichael
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, United Kingdom
| | - Michael Schrader
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, United Kingdom
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2
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Zimmermann R, Lang S, Lerner M, Förster F, Nguyen D, Helms V, Schrul B. Quantitative Proteomics and Differential Protein Abundance Analysis after the Depletion of PEX3 from Human Cells Identifies Additional Aspects of Protein Targeting to the ER. Int J Mol Sci 2021; 22:ijms222313028. [PMID: 34884833 PMCID: PMC8658024 DOI: 10.3390/ijms222313028] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/19/2021] [Accepted: 11/29/2021] [Indexed: 12/12/2022] Open
Abstract
Protein import into the endoplasmic reticulum (ER) is the first step in the biogenesis of around 10,000 different soluble and membrane proteins in humans. It involves the co- or post-translational targeting of precursor polypeptides to the ER, and their subsequent membrane insertion or translocation. So far, three pathways for the ER targeting of precursor polypeptides and four pathways for the ER targeting of mRNAs have been described. Typically, these pathways deliver their substrates to the Sec61 polypeptide-conducting channel in the ER membrane. Next, the precursor polypeptides are inserted into the ER membrane or translocated into the ER lumen, which may involve auxiliary translocation components, such as the TRAP and Sec62/Sec63 complexes, or auxiliary membrane protein insertases, such as EMC and the TMCO1 complex. Recently, the PEX19/PEX3-dependent pathway, which has a well-known function in targeting and inserting various peroxisomal membrane proteins into pre-existent peroxisomal membranes, was also found to act in the targeting and, putatively, insertion of monotopic hairpin proteins into the ER. These either remain in the ER as resident ER membrane proteins, or are pinched off from the ER as components of new lipid droplets. Therefore, the question arose as to whether this pathway may play a more general role in ER protein targeting, i.e., whether it represents a fourth pathway for the ER targeting of precursor polypeptides. Thus, we addressed the client spectrum of the PEX19/PEX3-dependent pathway in both PEX3-depleted HeLa cells and PEX3-deficient Zellweger patient fibroblasts by an established approach which involved the label-free quantitative mass spectrometry of the total proteome of depleted or deficient cells, as well as differential protein abundance analysis. The negatively affected proteins included twelve peroxisomal proteins and two hairpin proteins of the ER, thus confirming two previously identified classes of putative PEX19/PEX3 clients in human cells. Interestingly, fourteen collagen-related proteins with signal peptides or N-terminal transmembrane helices belonging to the secretory pathway were also negatively affected by PEX3 deficiency, which may suggest compromised collagen biogenesis as a hitherto-unknown contributor to organ failures in the respective Zellweger patients.
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Affiliation(s)
- Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.L.); (M.L.)
- Correspondence: (R.Z.); (B.S.)
| | - Sven Lang
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.L.); (M.L.)
| | - Monika Lerner
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.L.); (M.L.)
| | - Friedrich Förster
- Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands;
| | - Duy Nguyen
- Center for Bioinformatics, Saarland Informatics Campus, Saarland University, 66041 Saarbrücken, Germany; (D.N.); (V.H.)
| | - Volkhard Helms
- Center for Bioinformatics, Saarland Informatics Campus, Saarland University, 66041 Saarbrücken, Germany; (D.N.); (V.H.)
| | - Bianca Schrul
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (S.L.); (M.L.)
- Correspondence: (R.Z.); (B.S.)
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3
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Krikken AM, Wu H, de Boer R, Devos DP, Levine TP, van der Klei IJ. Peroxisome retention involves Inp1-dependent peroxisome-plasma membrane contact sites in yeast. J Cell Biol 2020; 219:152028. [PMID: 32805027 PMCID: PMC7659721 DOI: 10.1083/jcb.201906023] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 03/15/2020] [Accepted: 06/23/2020] [Indexed: 02/07/2023] Open
Abstract
Retention of peroxisomes in yeast mother cells requires Inp1, which is recruited to the organelle by the peroxisomal membrane protein Pex3. Here we show that Hansenula polymorpha Inp1 associates peroxisomes to the plasma membrane. Peroxisome-plasma membrane contact sites disappear upon deletion of INP1 but increase upon INP1 overexpression. Analysis of truncated Inp1 variants showed that the C terminus is important for association to the peroxisome, while a stretch of conserved positive charges and a central pleckstrin homology-like domain are important for plasma membrane binding. In cells of a PEX3 deletion, strain Inp1-GFP localizes to the plasma membrane, concentrated in patches near the bud neck and in the cortex of nascent buds. Upon disruption of the actin cytoskeleton by treatment of the cells with latrunculin A, Inp1-GFP became cytosolic, indicating that Inp1 localization is dependent on the presence of an intact actin cytoskeleton.
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Affiliation(s)
- Arjen M Krikken
- Molecular Cell Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Huala Wu
- Molecular Cell Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Rinse de Boer
- Molecular Cell Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Damien P Devos
- Centro Andaluz de Biología del Desarrollo, Consejo Superior de Investigaciones Científicas, Pablo de Olavide University, Seville, Spain
| | - Tim P Levine
- Institute of Ophthalmology, University College London, London, UK
| | - Ida J van der Klei
- Molecular Cell Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
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4
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Jiao T, Yang TT, Wang D, Gao ZQ, Wang JL, Tang BP, Liu QN, Zhang DZ, Dai LS. Characterization and expression analysis of immune-related genes in the red swamp crayfish, Procambarus clarkii in response to lipopolysaccharide challenge. FISH & SHELLFISH IMMUNOLOGY 2019; 95:140-150. [PMID: 31629063 DOI: 10.1016/j.fsi.2019.09.072] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/27/2019] [Accepted: 09/30/2019] [Indexed: 06/10/2023]
Abstract
To learn more about red swamp crayfish related genes in response to bacterial infections, we investigated immune-related genes induced by lipopolysaccharide (LPS) in the hepatopancreas using high-throughput sequencing method. In present the study, a total of 55,107 unigenes were identified, with an average length of 678 bp. A total of 2215 differentially expressed genes (DEGs) were found, including 669 up-regulated genes and 1546 down-regulated genes. The result of Gene ontology (GO) analysis revealed that 3017 DEGs were enriched in 19 biological process subcategories, 17 cellular component subcategories and 15 molecular function subcategories. The top 20 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways showed that "ribosome" was the most abundant group, which had 34 DEGs. KEGG enrichment analysis identified several immune response pathways. Real-time quantitative reverse transcription-PCR (qRT-PCR) results exhibited that several immune responsive genes were greatly up-regulated following LPS stimulation as observed in the results of high-throughput sequencing. Overall, this study provides new insight into the immune defense mechanisms of P. clarkii against LPS infection.
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Affiliation(s)
- Ting Jiao
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Synthetic Innovation Center for Coastal Bio-agriculture, Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, School of Ocean and Biological Engineering, Yancheng Teachers University, Yancheng, 224007, PR China; School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, 325035, PR China
| | - Ting-Ting Yang
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Synthetic Innovation Center for Coastal Bio-agriculture, Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, School of Ocean and Biological Engineering, Yancheng Teachers University, Yancheng, 224007, PR China; Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, PR China; College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing, 210009, PR China
| | - Dong Wang
- Instrumental Analysis Center, Yancheng Teachers University, Yancheng, 224007, PR China
| | - Zhen-Qiu Gao
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Synthetic Innovation Center for Coastal Bio-agriculture, Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, School of Ocean and Biological Engineering, Yancheng Teachers University, Yancheng, 224007, PR China; School of Pharmacy, Yancheng Teachers University, Yancheng, 224007, PR China
| | - Jia-Lian Wang
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Synthetic Innovation Center for Coastal Bio-agriculture, Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, School of Ocean and Biological Engineering, Yancheng Teachers University, Yancheng, 224007, PR China
| | - Bo-Ping Tang
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Synthetic Innovation Center for Coastal Bio-agriculture, Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, School of Ocean and Biological Engineering, Yancheng Teachers University, Yancheng, 224007, PR China
| | - Qiu-Ning Liu
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Synthetic Innovation Center for Coastal Bio-agriculture, Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, School of Ocean and Biological Engineering, Yancheng Teachers University, Yancheng, 224007, PR China; Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, PR China.
| | - Dai-Zhen Zhang
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Synthetic Innovation Center for Coastal Bio-agriculture, Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, School of Ocean and Biological Engineering, Yancheng Teachers University, Yancheng, 224007, PR China.
| | - Li-Shang Dai
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, 325035, PR China.
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5
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Jansen RLM, Klei IJ. The peroxisome biogenesis factors Pex3 and Pex19: multitasking proteins with disputed functions. FEBS Lett 2019; 593:457-474. [DOI: 10.1002/1873-3468.13340] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 02/06/2019] [Accepted: 02/12/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Renate L. M. Jansen
- Molecular Cell Biology Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen The Netherlands
| | - Ida J. Klei
- Molecular Cell Biology Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen The Netherlands
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6
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Farré JC, Mahalingam SS, Proietto M, Subramani S. Peroxisome biogenesis, membrane contact sites, and quality control. EMBO Rep 2018; 20:embr.201846864. [PMID: 30530632 DOI: 10.15252/embr.201846864] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Revised: 10/08/2018] [Accepted: 11/16/2018] [Indexed: 12/19/2022] Open
Abstract
Peroxisomes are conserved organelles of eukaryotic cells with important roles in cellular metabolism, human health, redox homeostasis, as well as intracellular metabolite transfer and signaling. We review here the current status of the different co-existing modes of biogenesis of peroxisomal membrane proteins demonstrating the fascinating adaptability in their targeting and sorting pathways. While earlier studies focused on peroxisomes as autonomous organelles, the necessity of the ER and potentially even mitochondria as sources of peroxisomal membrane proteins and lipids has come to light in recent years. Additionally, the intimate physical juxtaposition of peroxisomes with other organelles has transitioned from being viewed as random encounters to a growing appreciation of the expanding roles of such inter-organellar membrane contact sites in metabolic and regulatory functions. Peroxisomal quality control mechanisms have also come of age with a variety of mechanisms operating both during biogenesis and in the cellular response to environmental cues.
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Affiliation(s)
- Jean-Claude Farré
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, CA, USA
| | - Shanmuga S Mahalingam
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, CA, USA
| | - Marco Proietto
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, CA, USA
| | - Suresh Subramani
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, CA, USA
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7
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Wu H, de Boer R, Krikken AM, Akşit A, Yuan W, van der Klei IJ. Peroxisome development in yeast is associated with the formation of Pex3-dependent peroxisome-vacuole contact sites. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1866:349-359. [PMID: 30595161 DOI: 10.1016/j.bbamcr.2018.08.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 08/28/2018] [Accepted: 08/30/2018] [Indexed: 12/29/2022]
Abstract
Using electron and fluorescence microscopy techniques, we identified various physical contacts between peroxisomes and other cell organelles in the yeast Hansenula polymorpha. In exponential glucose-grown cells, which typically contain a single small peroxisome, contacts were only observed with the endoplasmic reticulum and the plasma membrane. Here we focus on a novel peroxisome-vacuole contact site that is formed when glucose-grown cells are shifted to methanol containing media, conditions that induce strong peroxisome development. At these conditions, the small peroxisomes rapidly increase in size, a phenomenon that is paralleled by the formation of distinct intimate contacts with the vacuole. Localization studies showed that the peroxin Pex3 accumulated in patches at the peroxisome-vacuole contact sites. In wild-type cells growing exponentially on medium containing glucose, peroxisome-vacuole contact sites were never observed. However, upon overproduction of Pex3 peroxisomes also associated to vacuoles at these growth conditions. Our observations strongly suggest a role for Pex3 in the formation of a novel peroxisome-vacuole contact site. This contact likely plays a role in membrane growth as it is formed solely at conditions of strong peroxisome expansion.
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Affiliation(s)
- Huala Wu
- Molecular Cell Biology, University of Groningen, PO Box 11103, 9300, CC, Groningen, the Netherlands
| | - Rinse de Boer
- Molecular Cell Biology, University of Groningen, PO Box 11103, 9300, CC, Groningen, the Netherlands
| | - Arjen M Krikken
- Molecular Cell Biology, University of Groningen, PO Box 11103, 9300, CC, Groningen, the Netherlands
| | - Arman Akşit
- Molecular Cell Biology, University of Groningen, PO Box 11103, 9300, CC, Groningen, the Netherlands
| | - Wei Yuan
- Molecular Cell Biology, University of Groningen, PO Box 11103, 9300, CC, Groningen, the Netherlands
| | - Ida J van der Klei
- Molecular Cell Biology, University of Groningen, PO Box 11103, 9300, CC, Groningen, the Netherlands.
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8
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Colasante C, Chen J, Ahlemeyer B, Bonilla-Martinez R, Karnati S, Baumgart-Vogt E. New insights into the distribution, protein abundance and subcellular localisation of the endogenous peroxisomal biogenesis proteins PEX3 and PEX19 in different organs and cell types of the adult mouse. PLoS One 2017; 12:e0183150. [PMID: 28817674 PMCID: PMC5560687 DOI: 10.1371/journal.pone.0183150] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 07/31/2017] [Indexed: 11/19/2022] Open
Abstract
Peroxisomes are ubiquitous organelles mainly involved in ROS and lipid metabolism. Their abundance, protein composition and metabolic function vary depending on the cell type and adjust to different intracellular and environmental factors such as oxidative stress or nutrition. The biogenesis and proliferation of these important organelles are regulated by proteins belonging to the peroxin (PEX) family. PEX3, an integral peroxisomal membrane protein, and the cytosolic shuttling receptor PEX19 are thought to be responsible for the early steps of peroxisome biogenesis and assembly of their matrix protein import machinery. Recently, both peroxins were suggested to be also involved in the autophagy of peroxisomes (pexophagy). Despite the fact that distribution and intracellular abundance of these proteins might regulate the turnover of the peroxisomal compartment in a cell type-specific manner, a comprehensive analysis of the endogenous PEX3 and PEX19 distribution in different organs is still missing. In this study, we have therefore generated antibodies against endogenous mouse PEX3 and PEX19 and analysed their abundance and subcellular localisation in various mouse organs, tissues and cell types and compared it to the one of three commonly used peroxisomal markers (PEX14, ABCD3 and catalase). Our results revealed that the abundance of PEX3, PEX19, PEX14, ABCD3 and catalase strongly varies in the analysed organs and cell types, suggesting that peroxisome abundance, biogenesis and matrix protein import are independently regulated. We further found that in some organs, such as heart and skeletal muscle, the majority of the shuttling receptor PEX19 is bound to the peroxisomal membrane and that a strong variability exists in the cell type-specific ratio of cytosol- and peroxisome-associated PEX19. In conclusion, our results indicate that peroxisomes in various cell types are heterogeneous with regards to their matrix, membrane and biogenesis proteins.
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Affiliation(s)
- Claudia Colasante
- Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University of Giessen, Giessen, Germany
| | - Jiangping Chen
- Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University of Giessen, Giessen, Germany
| | - Barbara Ahlemeyer
- Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University of Giessen, Giessen, Germany
| | - Rocio Bonilla-Martinez
- Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University of Giessen, Giessen, Germany
| | - Srikanth Karnati
- Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University of Giessen, Giessen, Germany
| | - Eveline Baumgart-Vogt
- Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University of Giessen, Giessen, Germany
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9
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Dias AF, Rodrigues TA, Pedrosa AG, Barros-Barbosa A, Francisco T, Azevedo JE. The peroxisomal matrix protein translocon is a large cavity-forming protein assembly into which PEX5 protein enters to release its cargo. J Biol Chem 2017; 292:15287-15300. [PMID: 28765278 DOI: 10.1074/jbc.m117.805044] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 07/26/2017] [Indexed: 12/18/2022] Open
Abstract
A remarkable property of the machinery for import of peroxisomal matrix proteins is that it can accept already folded proteins as substrates. This import involves binding of newly synthesized proteins by cytosolic peroxisomal biogenesis factor 5 (PEX5) followed by insertion of the PEX5-cargo complex into the peroxisomal membrane at the docking/translocation module (DTM). However, how these processes occur remains largely unknown. Here, we used truncated PEX5 molecules to probe the DTM architecture. We found that the DTM can accommodate a larger number of truncated PEX5 molecules comprising amino acid residues 1-197 than full-length PEX5 molecules. A shorter PEX5 version (PEX5(1-125)) still interacted correctly with the DTM; however, this species was largely accessible to exogenously added proteinase K, suggesting that this protease can access the DTM occupied by a small PEX5 protein. Interestingly, the PEX5(1-125)-DTM interaction was inhibited by a polypeptide comprising PEX5 residues 138-639. Apparently, the DTM can recruit soluble PEX5 through interactions with different PEX5 domains, suggesting that the PEX5-DTM interactions are to some degree fuzzy. Finally, we found that the interaction between PEX5 and PEX14, a major DTM component, is stable at pH 11.5. Thus, there is no reason to assume that the hitherto intriguing resistance of DTM-bound PEX5 to alkaline extraction reflects its direct contact with the peroxisomal lipid bilayer. Collectively, these results suggest that the DTM is best described as a large cavity-forming protein assembly into which cytosolic PEX5 can enter to release its cargo.
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Affiliation(s)
- Ana F Dias
- From the Instituto de Investigação e Inovação em Saúde (i3S) and.,the Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal and.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Tony A Rodrigues
- From the Instituto de Investigação e Inovação em Saúde (i3S) and.,the Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal and.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Ana G Pedrosa
- From the Instituto de Investigação e Inovação em Saúde (i3S) and.,the Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal and.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Aurora Barros-Barbosa
- From the Instituto de Investigação e Inovação em Saúde (i3S) and.,the Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal and
| | - Tânia Francisco
- From the Instituto de Investigação e Inovação em Saúde (i3S) and.,the Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal and
| | - Jorge E Azevedo
- From the Instituto de Investigação e Inovação em Saúde (i3S) and .,the Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal and.,Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
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10
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Giannopoulou EA, Emmanouilidis L, Sattler M, Dodt G, Wilmanns M. Towards the molecular mechanism of the integration of peroxisomal membrane proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:863-9. [PMID: 26434995 PMCID: PMC4819957 DOI: 10.1016/j.bbamcr.2015.09.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 09/22/2015] [Accepted: 09/28/2015] [Indexed: 11/30/2022]
Abstract
The correct topogenesis of peroxisomal membrane proteins is a crucial step for the formation of functioning peroxisomes. Although this process has been widely studied, the exact mechanism with which it occurs has not yet been fully characterized. Nevertheless, it is generally accepted that peroxisomes employ three proteins – Pex3, Pex19 and Pex16 in mammals – for the insertion of peroxisomal membrane proteins into the peroxisomal membrane. Structural biology approaches have been utilized for the elucidation of the mechanistic questions of peroxisome biogenesis, mainly by providing information on the architecture of the proteins significant for this process. This review aims to summarize, compare and put into perspective the structural knowledge that has been generated mainly for Pex3 and Pex19 and their interaction partners in recent years. This article is part of a Special Issue entitled: Peroxisomes edited by Ralf Erdmann. Structures of the PMP insertion factors Pex3 and Pex19 and their interactions with other protein ligands Structural insights provide a mechanistic understanding of the PMP functional network. Functional implications of structural order/disorder transitions
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Affiliation(s)
| | - Leonidas Emmanouilidis
- Institute of Structural Biology, Helmholtz Zentrum München, 85764 Neuherberg, Germany; Center for Integrated Protein Science Munich (CIPSM) at Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Zentrum München, 85764 Neuherberg, Germany; Center for Integrated Protein Science Munich (CIPSM) at Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany
| | - Gabriele Dodt
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany
| | - Matthias Wilmanns
- EMBL Hamburg, c/o DESY, Building 25A, Notkestraße 85, 22603 Hamburg, Germany; University of Hamburg Clinical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany.
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11
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Targeting and insertion of peroxisomal membrane proteins: ER trafficking versus direct delivery to peroxisomes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:870-80. [PMID: 26392202 DOI: 10.1016/j.bbamcr.2015.09.021] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2015] [Revised: 09/11/2015] [Accepted: 09/16/2015] [Indexed: 12/11/2022]
Abstract
The importance of peroxisomes is highlighted by severe inherited human disorders linked to impaired peroxisomal biogenesis. Besides the simple architecture of these ubiquitous and dynamic organelles, their biogenesis is surprisingly complex and involves specialized proteins, termed peroxins, which mediate targeting and insertion of peroxisomal membrane proteins (PMPs) into the peroxisomal bilayer, and the import of soluble proteins into the protein-dense matrix of the organelle. The long-standing paradigm that all peroxisomal proteins are imported directly into preexisting peroxisomes has been challenged by the detection of PMPs inside the endoplasmic reticulum (ER). New models propose that the ER originates peroxisomal biogenesis by mediating PMP trafficking to the peroxisomes via budding vesicles. However, the relative contribution of this ER-derived pathway to the total peroxisome population in vivo, and the detailed mechanisms of ER entry and exit of PMPs are controversially discussed. This review aims to summarize present knowledge about how PMPs are targeted to the ER, instead of being inserted directly into preexisting peroxisomes. Moreover, molecular mechanisms that facilitate bilayer insertion of PMPs among different species are discussed.
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Kim PK, Hettema EH. Multiple pathways for protein transport to peroxisomes. J Mol Biol 2015; 427:1176-90. [PMID: 25681696 PMCID: PMC4726662 DOI: 10.1016/j.jmb.2015.02.005] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 02/05/2015] [Accepted: 02/06/2015] [Indexed: 12/15/2022]
Abstract
Peroxisomes are unique among the organelles of the endomembrane system. Unlike other organelles that derive most if not all of their proteins from the ER (endoplasmic reticulum), peroxisomes contain dedicated machineries for import of matrix proteins and insertion of membrane proteins. However, peroxisomes are also able to import a subset of their membrane proteins from the ER. One aspect of peroxisome biology that has remained ill defined is the role the various import pathways play in peroxisome maintenance. In this review, we discuss the available data on matrix and membrane protein import into peroxisomes. Peroxisomal membrane and matrix proteins require distinct factors for their transport. Matrix proteins fold in the cytosol prior to their import. Loaded targeting receptors form part of the matrix protein translocation pore. Many membrane proteins are directly inserted into the peroxisomal membrane. Some peroxisomal membrane proteins are transported via the ER to peroxisomes.
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Affiliation(s)
- P K Kim
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON, Canada M5G 1X8; Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
| | - E H Hettema
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, South Yorkshire S10 2TN, United Kingdom.
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Chen Y, Pieuchot L, Loh RA, Yang J, Kari TMA, Wong JY, Jedd G. Hydrophobic handoff for direct delivery of peroxisome tail-anchored proteins. Nat Commun 2014; 5:5790. [PMID: 25517356 DOI: 10.1038/ncomms6790] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 11/04/2014] [Indexed: 02/06/2023] Open
Abstract
Tail-anchored (TA) proteins are inserted into membranes post-translationally through a C-terminal transmembrane domain (TMD). The PEX19 protein binds peroxisome TA proteins in the cytoplasm and delivers them to the membrane through the PEX3 receptor protein. An amphipathic segment in PEX19 promotes docking on PEX3. However, how this leads to substrate insertion is unknown. Here we reconstitute peroxisome TA protein biogenesis into two sequential steps of substrate TMD engagement and membrane insertion. We identify a series of previously uncharacterized amphipathic segments in PEX19 and identify one whose hydrophobicity is required for membrane insertion, but not TMD chaperone activity or PEX3 binding. A membrane-proximal hydrophobic surface of PEX3 promotes an unconventional form of membrane intercalation, and is also required for TMD insertion. Together, these data support a mechanism in which hydrophobic moieties in the TMD chaperone and its membrane-associated receptor act in a concerted manner to prompt TMD release and membrane insertion.
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Affiliation(s)
- Yinxiao Chen
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Laurent Pieuchot
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Rachel Ann Loh
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Jing Yang
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Teuku Mahfuzh Aufar Kari
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Jie Yun Wong
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Gregory Jedd
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
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Alteration of energy metabolism gene expression in cumulus cells affects oocyte maturation via MOS–mitogen-activated protein kinase pathway in dairy cows with an unfavorable “Fertil−” haplotype of one female fertility quantitative trait locus. Theriogenology 2014; 81:599-612. [DOI: 10.1016/j.theriogenology.2013.11.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 11/17/2013] [Accepted: 11/18/2013] [Indexed: 11/24/2022]
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Postfixation detergent treatment liberates the membrane modelling protein Pex11β from peroxisomal membranes. Histochem Cell Biol 2012; 138:541-7. [PMID: 22875152 DOI: 10.1007/s00418-012-1010-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/25/2012] [Indexed: 10/28/2022]
Abstract
Pex11 proteins are involved in membrane remodelling processes of peroxisomes, and are key components of peroxisomal division and proliferation. In mammals, three Pex11 isoforms, Pex11α, Pex11β, and Pex11γ exist. Here we demonstrate that Pex11β, but not Pex11α or Pex11γ, is almost exclusively extracted from peroxisomal membranes of paraformaldehyde-fixed cells by permeabilisation with the non-ionic detergent Triton X-100. This results in diminished detection of Myc-Pex11β in immunofluorescence preparations and appearance of the protein in the Triton X-100 extract. To our knowledge, Pex11β is the first peroxisomal membrane protein showing such a peculiar behaviour. Loss of Pex11β can be avoided by permeabilisation with digitonin, the addition of glutaraldehyde to the fixative, or the expression of a Pex11 fusion protein with a larger protein tag (e.g. YFP). Our observations further point to different functions and biochemical properties of the Pex11 isoforms within the peroxisomal membrane and during peroxisome proliferation.
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Waterham HR, Ebberink MS. Genetics and molecular basis of human peroxisome biogenesis disorders. Biochim Biophys Acta Mol Basis Dis 2012; 1822:1430-41. [PMID: 22871920 DOI: 10.1016/j.bbadis.2012.04.006] [Citation(s) in RCA: 160] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 03/30/2012] [Accepted: 04/11/2012] [Indexed: 10/28/2022]
Abstract
Human peroxisome biogenesis disorders (PBDs) are a heterogeneous group of autosomal recessive disorders comprised of two clinically distinct subtypes: the Zellweger syndrome spectrum (ZSS) disorders and rhizomelic chondrodysplasia punctata (RCDP) type 1. PBDs are caused by defects in any of at least 14 different PEX genes, which encode proteins involved in peroxisome assembly and proliferation. Thirteen of these genes are associated with ZSS disorders. The genetic heterogeneity among PBDs and the inability to predict from the biochemical and clinical phenotype of a patient with ZSS which of the currently known 13 PEX genes is defective, has fostered the development of different strategies to identify the causative gene defects. These include PEX cDNA transfection complementation assays followed by sequencing of the thus identified PEX genes, and a PEX gene screen in which the most frequently mutated exons of the different PEX genes are analyzed. The benefits of DNA testing for PBDs include carrier testing of relatives, early prenatal testing or preimplantation genetic diagnosis in families with a recurrence risk for ZSS disorders, and insight in genotype-phenotype correlations, which may eventually assist to improve patient management. In this review we describe the current status of genetic analysis and the molecular basis of PBDs.
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Grou CP, Francisco T, Rodrigues TA, Freitas MO, Pinto MP, Carvalho AF, Domingues P, Wood SA, Rodríguez-Borges JE, Sá-Miranda C, Fransen M, Azevedo JE. Identification of ubiquitin-specific protease 9X (USP9X) as a deubiquitinase acting on ubiquitin-peroxin 5 (PEX5) thioester conjugate. J Biol Chem 2012; 287:12815-27. [PMID: 22371489 DOI: 10.1074/jbc.m112.340158] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Peroxin 5 (PEX5), the peroxisomal protein shuttling receptor, binds newly synthesized peroxisomal matrix proteins in the cytosol and promotes their translocation across the organelle membrane. During the translocation step, PEX5 itself becomes inserted into the peroxisomal docking/translocation machinery. PEX5 is then monoubiquitinated at a conserved cysteine residue and extracted back into the cytosol in an ATP-dependent manner. We have previously shown that the ubiquitin-PEX5 thioester conjugate (Ub-PEX5) released into the cytosol can be efficiently disrupted by physiological concentrations of glutathione, raising the possibility that a fraction of Ub-PEX5 is nonenzymatically deubiquitinated in vivo. However, data suggesting that Ub-PEX5 is also a target of a deubiquitinase were also obtained in that work. Here, we used an unbiased biochemical approach to identify this enzyme. Our results suggest that ubiquitin-specific protease 9X (USP9X) is by far the most active deubiquitinase acting on Ub-PEX5, both in female rat liver and HeLa cells. We also show that USP9X is an elongated monomeric protein with the capacity to hydrolyze thioester, isopeptide, and peptide bonds. The strategy described here will be useful in identifying deubiquitinases acting on other ubiquitin conjugates.
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Affiliation(s)
- Cláudia P Grou
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal
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Fox MA, Walsh LA, Nieuwesteeg M, Damjanovski S. PEX11β induces peroxisomal gene expression and alters peroxisome number during early Xenopus laevis development. BMC DEVELOPMENTAL BIOLOGY 2011; 11:24. [PMID: 21526995 PMCID: PMC3095563 DOI: 10.1186/1471-213x-11-24] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Accepted: 04/28/2011] [Indexed: 01/04/2023]
Abstract
Background Peroxisomes are organelles whose roles in fatty acid metabolism and reactive oxygen species elimination have contributed much attention in understanding their origin and biogenesis. Many studies have shown that de novo peroxisome biogenesis is an important regulatory process, while yeast studies suggest that total peroxisome numbers are in part regulated by proteins such as Pex11, which can facilitate the division of existing peroxisomes. Although de novo biogenesis and divisions are likely important mechanisms, the regulation of peroxisome numbers during embryonic development is poorly understood. Peroxisome number and function are particularly crucial in oviparous animals such as frogs where large embryonic yolk and fatty acid stores must be quickly metabolized, and resulting reactive oxygen species eliminated. Here we elucidate the role of Pex11β in regulating peroxisomal gene expression and number in Xenopus laevis embryogenesis. Results Microinjecting haemagglutinin (HA) tagged Pex11β in early embryos resulted in increased RNA levels for peroxisome related genes PMP70 and catalase at developmental stages 10 and 20, versus uninjected embryos. Catalase and PMP70 proteins were found in punctate structures at stage 20 in control embryos, whereas the injection of ectopic HA-Pex11β induced their earlier localization in punctate structures at stage 10. Furthermore, the peroxisomal marker GFP-SKL, which was found localized as peroxisome-like structures at stage 20, was similarly found at stage 10 when co-microinjected with HA-Pex11β. Conclusions Overexpressed Pex11β altered peroxisomal gene levels and induced the early formation of peroxisomes-like structures during development, both of which demonstrate that Pex11β may be a key regulator of peroxisome number in early Xenopus embryos.
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Affiliation(s)
- Mark A Fox
- Department of Biology, University of Western Ontario, 3053 Biological and Geological Sciences Building, 1151 Richmond Street North, London, ON, N6A 5B7, Canada
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Sato Y, Shibata H, Nakatsu T, Nakano H, Kashiwayama Y, Imanaka T, Kato H. Structural basis for docking of peroxisomal membrane protein carrier Pex19p onto its receptor Pex3p. EMBO J 2010; 29:4083-93. [PMID: 21102411 PMCID: PMC3018794 DOI: 10.1038/emboj.2010.293] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Accepted: 11/02/2010] [Indexed: 01/07/2023] Open
Abstract
Peroxisomes require peroxin (Pex) proteins for their biogenesis. The interaction between Pex3p, which resides on the peroxisomal membrane, and Pex19p, which resides in the cytosol, is crucial for peroxisome formation and the post-translational targeting of peroxisomal membrane proteins (PMPs). It is not known how Pex3p promotes the specific interaction with Pex19p for the purpose of PMP translocation. Here, we present the three-dimensional structure of the complex between a cytosolic domain of Pex3p and the binding-region peptide of Pex19p. The overall shape of Pex3p is a prolate spheroid with a novel fold, the 'twisted six-helix bundle.' The Pex19p-binding site is at an apex of the Pex3p spheroid. A 16-residue region of the Pex19p peptide forms an α-helix and makes a contact with Pex3p; this helix is disordered in the unbound state. The Pex19p peptide contains a characteristic motif, consisting of the leucine triad (Leu18, Leu21, Leu22), and Phe29, which are critical for the Pex3p binding and peroxisome biogenesis.
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Affiliation(s)
- Yasuhiko Sato
- Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Hiroyuki Shibata
- Department of Cardiac Physiology, National Cardiovascular Center Research Institute, Osaka, Japan
| | - Toru Nakatsu
- Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan,RIKEN SPring-8 Center, Hyogo, Japan
| | - Hiroaki Nakano
- Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Yoshinori Kashiwayama
- Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Tsuneo Imanaka
- Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Hiroaki Kato
- Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan,RIKEN SPring-8 Center, Hyogo, Japan,Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan. Tel.: +81 75 753 4617; Fax: +81 75 753 9272; E-mail:
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Schmidt F, Treiber N, Zocher G, Bjelic S, Steinmetz MO, Kalbacher H, Stehle T, Dodt G. Insights into peroxisome function from the structure of PEX3 in complex with a soluble fragment of PEX19. J Biol Chem 2010; 285:25410-7. [PMID: 20554521 PMCID: PMC2919104 DOI: 10.1074/jbc.m110.138503] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 05/17/2010] [Indexed: 11/06/2022] Open
Abstract
The human peroxins PEX3 and PEX19 play a central role in peroxisomal membrane biogenesis. The membrane-anchored PEX3 serves as the receptor for cytosolic PEX19, which in turn recognizes newly synthesized peroxisomal membrane proteins. After delivering these proteins to the peroxisomal membrane, PEX19 is recycled to the cytosol. The molecular mechanisms underlying these processes are not well understood. Here, we report the crystal structure of the cytosolic domain of PEX3 in complex with a PEX19-derived peptide. PEX3 adopts a novel fold that is best described as a large helical bundle. A hydrophobic groove at the membrane-distal end of PEX3 engages the PEX19 peptide with nanomolar affinity. Mutagenesis experiments identify phenylalanine 29 in PEX19 as critical for this interaction. Because key PEX3 residues involved in complex formation are highly conserved across species, the observed binding mechanism is of general biological relevance.
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Affiliation(s)
- Friederike Schmidt
- From the Interfaculty Institute for Biochemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Nora Treiber
- the Institute for Organic Chemistry and Biochemistry, University of Freiburg, 79106 Freiburg, Germany
| | - Georg Zocher
- From the Interfaculty Institute for Biochemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Sasa Bjelic
- the Laboratory of Biomolecular Research, Structural Biology, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland, and
| | - Michel O. Steinmetz
- the Laboratory of Biomolecular Research, Structural Biology, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland, and
| | - Hubert Kalbacher
- From the Interfaculty Institute for Biochemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Thilo Stehle
- From the Interfaculty Institute for Biochemistry, University of Tübingen, 72076 Tübingen, Germany
- the Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
| | - Gabriele Dodt
- From the Interfaculty Institute for Biochemistry, University of Tübingen, 72076 Tübingen, Germany
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