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Krayl M, Lim JH, Martin F, Guiard B, Voos W. A cooperative action of the ATP-dependent import motor complex and the inner membrane potential drives mitochondrial preprotein import. Mol Cell Biol 2006; 27:411-25. [PMID: 17074805 PMCID: PMC1800818 DOI: 10.1128/mcb.01391-06] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The import of mitochondrial preproteins requires an electric potential across the inner membrane and the hydrolysis of ATP in the matrix. We assessed the contributions of the two energy sources to the translocation driving force responsible for movement of the polypeptide chain through the translocation channel and the unfolding of preprotein domains. The import-driving activity was directly analyzed by the determination of the protease resistances of saturating amounts of membrane-spanning translocation intermediates. The ability to generate a strong translocation-driving force was solely dependent on the activity of the ATP-dependent import motor complex in the matrix. For a sustained import-driving activity on the preprotein in transit, an unstructured N-terminal segment of more than 70 to 80 amino acid residues was required. The electric potential of the inner membrane was required to maintain the import-driving activity at a high level. The electrophoretic force of the potential exhibited only a limited capacity to unfold preprotein domains. We conclude that the membrane potential increases the probability of a dynamic interaction of the preprotein with the import motor. Polypeptide translocation and unfolding are mainly driven by the inward-directed translocation activity based on the functional cooperation of the import motor components.
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Affiliation(s)
- Martin Krayl
- Institut für Biochemie und Molekularbiologie, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany
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2
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von Janowsky B, Knapp K, Major T, Krayl M, Guiard B, Voos W. Structural properties of substrate proteins determine their proteolysis by the mitochondrial AAA+ protease Pim1. Biol Chem 2006; 386:1307-17. [PMID: 16336126 DOI: 10.1515/bc.2005.149] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The protease Pim1/LON, a member of the AAA+ family of homo-oligomeric ATP-dependent proteases, is responsible for the degradation of soluble proteins in the mitochondrial matrix. To establish the molecular parameters required for the specific recognition and proteolysis of substrate proteins by Pim1, we analyzed the in organello degradation of imported reporter proteins containing different structural properties. The amino acid composition at the amino-terminal end had no major effect on the proteolysis reaction. However, proteins with an amino-terminal extension of less than 60 amino acids in front of a stably folded reporter domain were completely resistant to proteolysis by Pim1. Substrate proteins with a longer amino-terminal extension showed incomplete proteolysis, resulting in the generation of a defined degradation fragment. We conclude that Pim1-mediated protein degradation is processive and is initiated from an unstructured amino-terminal segment. Resistance to degradation and fragment formation was abolished if the folding state of the reporter domain was destabilized, indicating that Pim1 is not able to unravel folded proteins for proteolysis. We propose that the requirement for an exposed, large, non-native protein segment, in combination with a limited unfolding capability, accounts for the selectivity of the protease Pim1 for damaged or misfolded polypeptides.
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Affiliation(s)
- Birgit von Janowsky
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Str. 7, D-79104 Freiburg, Germany
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3
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Bade S, Rummel A, Reisinger C, Karnath T, Ahnert-Hilger G, Bigalke H, Binz T. Botulinum neurotoxin type D enables cytosolic delivery of enzymatically active cargo proteins to neurones via unfolded translocation intermediates. J Neurochem 2005; 91:1461-72. [PMID: 15584922 DOI: 10.1111/j.1471-4159.2004.02844.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Multi-domain bacterial protein toxins are being explored as potential carriers for targeted delivery of biomolecules. Previous approaches employing isolated receptor binding subunits disallow entry into the cytosol. Strategies in which catalytic domains are replaced with cargo molecules are presumably inefficient due to co-operation of domains during the endosomal translocation step. Here, we characterize a novel transport vehicle in which cargo proteins are attached to the amino terminus of the full-length botulinum neurotoxin type D (BoNT/D). The intrinsic enzymatic activity of the neurotoxin allowed quantification of the efficacy of cargo delivery to the cytosol. Dihydrofolate reductase and BoNT type A (BoNT/A) light chain (LC) were efficiently conveyed into the cytosol, whereas attachment of firefly luciferase or green fluorescent protein drastically reduced the toxicity. Luciferase and BoNT/A LC retained their catalytic activity as evidenced by luciferin conversion or SNAP-25 hydrolysis in the cytosol of synaptosomes, respectively. Conformationally stabilized dihydrofolate reductase as cargo considerably decreased the toxicity indicative for the requirement of partial unfolding of cargo protein and catalytic domain as prerequisite for efficient translocation across the endosomal membrane. Thus, enzymatically inactive clostridial neurotoxins may serve as effective, safe carriers for delivering proteins in functionally active form to the cytosol of neurones.
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Affiliation(s)
- Steffen Bade
- Institute für Biochemie, Medizinische Hochschule Hannover, Hannover, Germany
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Fischer G, Aumüller T. Regulation of peptide bond cis/trans isomerization by enzyme catalysis and its implication in physiological processes. Rev Physiol Biochem Pharmacol 2004; 148:105-50. [PMID: 12698322 DOI: 10.1007/s10254-003-0011-3] [Citation(s) in RCA: 189] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In some cases, the slow rotational movement underlying peptide bond cis/trans isomerizations is found to control the biological activity of proteins. Peptide bond cis/trans isomerases as cyclophilins, Fk506-binding proteins, parvulins, and bacterial hsp70 generally assist in the interconversion of the polypeptide substrate cis/trans isomers, and rate acceleration is the dominating mechanism of action in cells. We present evidence disputing the hypothesis that some of the molecular properties of these proteins play an auxiliary role in enzyme function.
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Affiliation(s)
- G Fischer
- Max Planck Research Unit for Enzymology of Protein Folding, Weinbergweg 22, 06120 Halle, Germany.
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Dugave C, Demange L. Cis-trans isomerization of organic molecules and biomolecules: implications and applications. Chem Rev 2003; 103:2475-532. [PMID: 12848578 DOI: 10.1021/cr0104375] [Citation(s) in RCA: 753] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Christophe Dugave
- CEA/Saclay, Département d'Ingénierie et d'Etudes des Protéines (DIEP), Bâtiment 152, 91191 Gif-sur-Yvette, France.
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Chakraborty A, Das I, Datta R, Sen B, Bhattacharyya D, Mandal C, Datta AK. A Single-domain Cyclophilin from Leishmania donovaniReactivates Soluble Aggregates of Adenosine Kinase by Isomerase-independent Chaperone Function. J Biol Chem 2002; 277:47451-60. [PMID: 12244046 DOI: 10.1074/jbc.m204827200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Disaggregation and reactivation of aggregated proteins by chaperones is well established. However, little is known regarding such kind of function of single-domain small cyclophilins (CyPs). Here we demonstrate that, with increasing concentrations, fully active adenosine kinase (AdK) of Leishmania donovani tends to form soluble aggregates, resulting in inactivation. Using this inactive enzyme as the substrate, it is shown that a CyP from L. donovani (LdCyP) alone can cause complete disaggregation, leading to reactivation of the enzyme. The reactivating ability of LdCyP remains unaffected even in the presence of cyclosporin A and macromolecular crowding agents. The reactivation occurs noncatalytically and is reversible. A truncated LdCyP, devoid of 88 amino acids from the N terminus, is found to be required in near stoichiometric proportion to reactivate AdK, suggesting essentiality of the C-terminal region. Gel filtration and light-scattering experiments together with protein cross-linking studies revealed that both full-length LdCyP and the truncated form directly interact with AdK and convert oligomeric forms of the enzyme to monomeric state. Homology modeling studies suggest that the exposed hydrophobic residues of LdCyP, by interacting with solvent-accessible hydrophobic surface of AdK, pull apart its aggregated inactive oligomers to functional monomers. Clearly, the results are consistent with the interpretation that the higher efficiency of the truncated LdCyP is most likely due to increased exposure of the hydrophobic residues on its surface. These observations, besides establishing L. donovani AdK as one of the model enzymes to study aggregation-disaggregation of proteins, raise the possibility that single-domain small CyPs, under physiological conditions, may regulate the activity of aggregation-prone proteins by ensuring their disaggregation.
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Affiliation(s)
- Anutosh Chakraborty
- Division of Infectious Diseases, Leishmania Group, Indian Institute of Chemical Biology, Kolkata 700 032, India
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Rottgers K, Zufall N, Guiard B, Voos W. The ClpB homolog Hsp78 is required for the efficient degradation of proteins in the mitochondrial matrix. J Biol Chem 2002; 277:45829-37. [PMID: 12237310 DOI: 10.1074/jbc.m207152200] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Molecular chaperones perform vital functions in mitochondrial protein import and folding. In yeast mitochondria, two members of the Clp/Hsp100 chaperone family, Hsp78 and Mcx1, have been identified as homologs of the bacterial proteins ClpB and ClpX, respectively. In this report we employed a novel quantitative assay system to assess the role of Hsp78 and Mcx1 in protein degradation within the matrix. Mitochondria were preloaded with large amounts of two purified recombinant reporter proteins exhibiting different folding stabilities. Proteolysis of the imported substrate proteins depended on the mitochondrial level of ATP and was mediated by the matrix protease Pim1/LON. Degradation rates were found to be independent of the folding stability of the reporter proteins. Mitochondria from hsp78Delta cells exhibited a significant defect in the degradation efficiency of both substrates even at low temperature whereas mcx1Delta mitochondria showed wild-type activity. The proteolysis defect in hsp78Delta mitochondria was independent from the aggregation behavior of the substrate proteins. We conclude that Hsp78 is a genuine component of the mitochondrial proteolysis system required for the efficient degradation of substrate proteins in the matrix.
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Affiliation(s)
- Karin Rottgers
- Institut für Biochemie und Molekularbiologie, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany
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Zhu WY, Bunni M, Priest DG, DiCapua JL, Dressler JM, Chen Z, Melera PW. Severe folate restriction results in depletion of and alteration in the composition of the intracellular folate pool, moderate sensitization to methotrexate and trimetrexate, upregulation of endogenous DHFR activity, and overexpression of metallothionein II and folate receptor alpha that, upon folate repletion, confer drug resistance to CHL cells. JOURNAL OF EXPERIMENTAL THERAPEUTICS AND ONCOLOGY 2002; 2:264-77. [PMID: 12416030 DOI: 10.1046/j.1359-4117.2002.01049.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
DC-3F/FA3 cells (FA3) were derived from antifolate-sensitive CHL cells by selection for growth in folate-free media containing 15 pM [6S]-5CHOFH4. These cells undergo a 30-fold decrease in intracellular folates, overexpress folate receptor alpha (FR alpha) and metallothionein II, and display increased sensitivity to the dihydrofolate reductase (DHFR) targeted anti-folates methotrexate (MTX) and trimetrexate (TMTX), which can be attributed primarily to the folate pool status. Upon folate repletion by growth in 15 nM [6S]-5CHOFH4, they display a 5- and 10-fold increase in resistance to both drugs, respectively, even though folate pools are restored by only 43%. Enforced overexpression of FR alpha in transfectants cultured in nanomolar folate did not confer resistance to MTX but did support a modest 2-fold increase in resistance to TMTX. Enforced overexpression of MTII had a similar effect, but when both were overexpressed together no increase in resistance beyond that conferred by each one separately was noted, suggesting that both confer resistance to TMTX through a common downstream mechanism. Analysis of three independent low folate selected clones, FA3, FA7, and FA14, showed that each had a 5- to 6-fold increase in DHFR activity accompanied by a similar increase in DHFR protein level. However, no differences were detected in the DHFR gene copy number or in the steady-state amount of DHFR mRNA, suggesting that a posttranscriptional mechanism was responsible for the increase in DHFR expression.
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Affiliation(s)
- Wei-Yong Zhu
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD 21201, USA
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Affiliation(s)
- F X Schmid
- Biochemisches Laboratorium, Universität Bayreuth, D-95440 Bayreuth, Germany
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Wallace LA, Robert Matthews C. Highly divergent dihydrofolate reductases conserve complex folding mechanisms. J Mol Biol 2002; 315:193-211. [PMID: 11779239 DOI: 10.1006/jmbi.2001.5230] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To test the hypothesis that protein folding mechanisms are better conserved than amino acid sequences, the mechanisms for dihydrofolate reductases (DHFR) from human (hs), Escherichia coli (ec) and Lactobacillus casei (lc) were elucidated and compared using intrinsic Trp fluorescence and fluorescence-detected 8-anilino-1-naphthalenesulfonate (ANS) binding. The development of the native state was monitored using either methotrexate (absorbance at 380 nm) or NADPH (extrinsic fluorescence) binding. All three homologs displayed complex unfolding and refolding kinetic mechanisms that involved partially folded states and multiple energy barriers. Although the pairwise sequence identities are less than 30 %, folding to the native state occurs via parallel folding channels and involves two types of on-pathway kinetic intermediates for all three homologs. The first ensemble of kinetic intermediates, detected within a few milliseconds, has significant secondary structure and exposed hydrophobic cores. The second ensemble is obligatory and has native-like side-chain packing in a hydrophobic core; however, these intermediates are unable to bind active-site ligands. The formation of the ensemble of native states occurs via three channels for hsDHFR, and four channels for lcDHFR and ecDHFR. The binding of active-site ligands (methotrexate and NADPH) accompanies the rate-limiting formation of the native ensemble. The conservation of the fast, intermediate and slow-folding events for this complex alpha/beta motif provides convincing evidence for the hypothesis that evolutionarily related proteins achieve the same fold via similar pathways.
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Affiliation(s)
- Louise A Wallace
- Department of Chemistry and Center for Biomolecular Structure and Function, The Pennsylvania State University, PA 16802, USA
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11
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Meisinger C, Ryan MT, Hill K, Model K, Lim JH, Sickmann A, Müller H, Meyer HE, Wagner R, Pfanner N. Protein import channel of the outer mitochondrial membrane: a highly stable Tom40-Tom22 core structure differentially interacts with preproteins, small tom proteins, and import receptors. Mol Cell Biol 2001; 21:2337-48. [PMID: 11259583 PMCID: PMC86867 DOI: 10.1128/mcb.21.7.2337-2348.2001] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The preprotein translocase of the yeast mitochondrial outer membrane (TOM) consists of the initial import receptors Tom70 and Tom20 and a approximately 400-kDa (400 K) general import pore (GIP) complex that includes the central receptor Tom22, the channel Tom40, and the three small Tom proteins Tom7, Tom6, and Tom5. We report that the GIP complex is a highly stable complex with an unusual resistance to urea and alkaline pH. Under mild conditions for mitochondrial lysis, the receptor Tom20, but not Tom70, is quantitatively associated with the GIP complex, forming a 500K to 600K TOM complex. A preprotein, stably arrested in the GIP complex, is released by urea but not high salt, indicating that ionic interactions are not essential for keeping the preprotein in the GIP complex. Under more stringent detergent conditions, however, Tom20 and all three small Tom proteins are released, while the preprotein remains in the GIP complex. Moreover, purified outer membrane vesicles devoid of translocase components of the intermembrane space and inner membrane efficiently accumulate the preprotein in the GIP complex. Together, Tom40 and Tom22 thus represent the functional core unit that stably holds accumulated preproteins. The GIP complex isolated from outer membranes exhibits characteristic TOM channel activity with two coupled conductance states, each corresponding to the activity of purified Tom40, suggesting that the complex contains two simultaneously active and coupled channel pores.
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Affiliation(s)
- C Meisinger
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Germany
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Lim JH, Martin F, Guiard B, Pfanner N, Voos W. The mitochondrial Hsp70-dependent import system actively unfolds preproteins and shortens the lag phase of translocation. EMBO J 2001; 20:941-50. [PMID: 11230118 PMCID: PMC145481 DOI: 10.1093/emboj/20.5.941] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Unfolding is an essential process during translocation of preproteins into mitochondria; however, controversy exists as to whether mitochondria play an active role in unfolding. We have established an in vitro system with a kinetic saturation of the mitochondrial import machinery, yielding translocation rates comparable to in vivo import rates. Preproteins with short N-terminal segments in front of a folded domain show a characteristic delay of the onset of translocation (lag phase) although the maximal import rate is similar to that of longer preproteins. The lag phase is shortened by extending the N-terminal segment to improve the accessibility to matrix heat shock protein 70 and abolished by unfolding of the preprotein. A mutant mtHsp70 defective in binding to the inner membrane prolongs the lag phase and reduces the translocation activity. A direct comparison of the rate of spontaneous unfolding in solution with that during translocation demonstrates that unfolding by mitochondria is significantly faster, proving an active unfolding process. We conclude that access of mtHsp70 to N-terminal preprotein segments is critical for active unfolding and initiation of translocation.
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Affiliation(s)
- Joo Hyun Lim
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Fakultät für Biologie, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany and Centre de Génétique Moléculaire, Laboratoire propre du CNRS associeté à l’Université Pierre et Marie Curie, 91190 Gif-sur-Yvette, France Present address: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel Corresponding author e-mail:
| | - Falk Martin
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Fakultät für Biologie, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany and Centre de Génétique Moléculaire, Laboratoire propre du CNRS associeté à l’Université Pierre et Marie Curie, 91190 Gif-sur-Yvette, France Present address: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel Corresponding author e-mail:
| | - Bernard Guiard
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Fakultät für Biologie, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany and Centre de Génétique Moléculaire, Laboratoire propre du CNRS associeté à l’Université Pierre et Marie Curie, 91190 Gif-sur-Yvette, France Present address: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel Corresponding author e-mail:
| | - Nikolaus Pfanner
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Fakultät für Biologie, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany and Centre de Génétique Moléculaire, Laboratoire propre du CNRS associeté à l’Université Pierre et Marie Curie, 91190 Gif-sur-Yvette, France Present address: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel Corresponding author e-mail:
| | - Wolfgang Voos
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Fakultät für Biologie, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany and Centre de Génétique Moléculaire, Laboratoire propre du CNRS associeté à l’Université Pierre et Marie Curie, 91190 Gif-sur-Yvette, France Present address: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel Corresponding author e-mail:
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