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Ozturk TN, Coumoundouros C, Culham DE, Wood JM. Structural Determinants and Functional Significance of Dimerization for Osmosensing Transporter ProP in Escherichia coli. Biochemistry 2023; 62:118-133. [PMID: 36516499 DOI: 10.1021/acs.biochem.2c00393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Osmosensing transporter ProP forestalls cellular dehydration by detecting environments with high osmotic pressure and mediating the accumulation of organic osmolytes by bacterial cells. It is composed of 12 transmembrane helices with cytoplasmic N- and C-termini. In Escherichia coli, dimers form when the C-terminal domains of ProP molecules form homodimeric, antiparallel, α-helical coiled coils. No dominant negative effect was detected when inactive and active ProP molecules formed heterodimers in vivo. Purification of ProP in detergent dodecylmaltoside yielded monomers, which were functional after reconstitution in proteoliposomes. With other evidence, this suggests that ProP monomers function independently whether in the monomeric or dimeric state. Amino acid replacements that disrupted or reversed the coiled coil did not prevent in vivo dimerization of ProP detected with a bacterial two-hybrid system. Maleimide labeling detected no osmolality-dependent variation in the reactivities of cysteine residues introduced to transmembrane helix (TM) XII. In contrast, coarse-grained molecular dynamic simulations detected deformation of the lipid around TMs III and VI, on the lipid-exposed protein surface opposite to TM XII. This suggests that the dimer interface of ProP includes the surfaces of TMs III and VI, not of TM XII as previously suggested by crosslinking data. Homology modeling suggested that coiled-coil formation and dimerization via such an interface are not mutually exclusive. In previous work, alterations to the C-terminal coiled coil blocked co-localization of ProP with phospholipid cardiolipin at E. coli cell poles. Thus, dimerization may contribute to ProP targeting, adjust its lipid environment, and hence indirectly modify its osmotic stress response.
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Affiliation(s)
- Tugba N Ozturk
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, Saint Louis, Missouri63110, United States.,Theoretical Molecular Biophysics Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland20814, United States
| | - Chelsea Coumoundouros
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, CanadaN1G 2 W1
| | - Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, CanadaN1G 2 W1
| | - Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, CanadaN1G 2 W1
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2
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Khera R, Mehdipour AR, Bolla JR, Kahnt J, Welsch S, Ermler U, Muenke C, Robinson CV, Hummer G, Xie H, Michel H. Cryo-EM structures of pentameric autoinducer-2 exporter from Escherichia coli reveal its transport mechanism. EMBO J 2022; 41:e109990. [PMID: 35698912 PMCID: PMC9475539 DOI: 10.15252/embj.2021109990] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 05/04/2022] [Accepted: 05/06/2022] [Indexed: 12/16/2022] Open
Abstract
Bacteria utilize small extracellular molecules to communicate in order to collectively coordinate their behaviors in response to the population density. Autoinducer-2 (AI-2), a universal molecule for both intra- and inter-species communication, is involved in the regulation of biofilm formation, virulence, motility, chemotaxis, and antibiotic resistance. While many studies have been devoted to understanding the biosynthesis and sensing of AI-2, very little information is available on its export. The protein TqsA from Escherichia coli, which belongs to the AI-2 exporter superfamily, has been shown to export AI-2. Here, we report the cryogenic electron microscopic structures of two AI-2 exporters (TqsA and YdiK) from E. coli at 3.35 Å and 2.80 Å resolutions, respectively. Our structures suggest that the AI-2 exporter exists as a homo-pentameric complex. In silico molecular docking and native mass spectrometry experiments were employed to demonstrate the interaction between AI-2 and TqsA, and the results highlight the functional importance of two helical hairpins in substrate binding. We propose that each monomer works as an independent functional unit utilizing an elevator-type transport mechanism.
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Affiliation(s)
- Radhika Khera
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Ahmad R Mehdipour
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.,Centre for molecular modelling, Ghent University, Zwijnaarde, Belgium
| | - Jani R Bolla
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK.,The Kavli Institute for Nanoscience Discovery, Oxford, UK.,Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Joerg Kahnt
- Core Facility for Mass Spectrometry and Proteomics, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Sonja Welsch
- Central Electron Microscopy Facility, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Ulrich Ermler
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Cornelia Muenke
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Carol V Robinson
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK.,The Kavli Institute for Nanoscience Discovery, Oxford, UK
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.,Institute of Biophysics, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Hao Xie
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Hartmut Michel
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
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3
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Genome-wide CRISPR screen reveals CLPTM1L as a lipid scramblase required for efficient glycosylphosphatidylinositol biosynthesis. Proc Natl Acad Sci U S A 2022; 119:e2115083119. [PMID: 35344438 PMCID: PMC9169118 DOI: 10.1073/pnas.2115083119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Scramblases translocate lipids across the lipid bilayer without consumption of ATP, thereby regulating lipid distributions in cellular membranes. Cytosol-to-lumen translocation across the endoplasmic reticulum (ER) membrane is a common process among lipid glycoconjugates involved in posttranslational protein modifications in eukaryotes. These translocations are thought to be mediated by specific ER-resident scramblases, but the identity of these proteins and the underlying molecular mechanisms have been elusive. Here, we show that CLPTM1L, an integral membrane protein with eight putative transmembrane domains, is the major lipid scramblase involved in efficient glycosylphosphatidylinositol biosynthesis in the ER membrane. Our results validate the long-standing hypothesis that lipid scramblases ensure the efficient translocations of lipid glycoconjugates across the ER membrane for protein glycosylation pathways. Glycosylphosphatidylinositols (GPIs) are complex glycolipids that act as membrane anchors of many eukaryotic cell surface proteins. Biosynthesis of GPIs is initiated at the cytosolic face of the endoplasmic reticulum (ER) by generation of N-acetylglucosaminyl-phosphatidylinositol (GlcNAc-PI). The second intermediate, glucosaminyl-phosphatidylinositol (GlcN-PI), is translocated across the membrane to the luminal face for later biosynthetic steps and attachment to proteins. The mechanism of the luminal translocation of GlcN-PI is unclear. Here, we report a genome-wide CRISPR knockout screen of genes required for rescuing GPI-anchored protein expression after addition of chemically synthesized GlcNAc-PI to PIGA-knockout cells that cannot synthesize GlcNAc-PI. We identified CLPTM1L (cleft lip and palate transmembrane protein 1-like), an ER-resident multipass membrane protein, as a GlcN-PI scramblase required for efficient biosynthesis of GPIs. Knockout of CLPTM1L in PIGA-knockout cells impaired the efficient utilization of chemically synthesized GlcNAc-PI and GlcN-PI for GPI biosynthesis. Purified CLPTM1L scrambled GlcN-PI, GlcNAc-PI, PI, and several other phospholipids in vitro. CLPTM1L, a member of the PQ-loop family of proteins, represents a type of lipid scramblase having no structural similarity to known lipid scramblases. Knockout of CLPTM1L in various wild-type mammalian cultured cells partially decreased the level of GPI-anchored proteins. These results suggest that CLPTM1L is the major lipid scramblase involved in cytosol-to-lumen translocation of GlcN-PI across the ER membrane for efficient GPI biosynthesis.
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Requirement of Xk and Vps13a for the P2X7-mediated phospholipid scrambling and cell lysis in mouse T cells. Proc Natl Acad Sci U S A 2022; 119:2119286119. [PMID: 35140185 PMCID: PMC8851519 DOI: 10.1073/pnas.2119286119] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/06/2022] [Indexed: 12/12/2022] Open
Abstract
A high extracellular adenosine triphosphate (ATP) concentration rapidly and reversibly exposes phosphatidylserine (PtdSer) in T cells by binding to the P2X7 receptor, which ultimately leads to necrosis. Using mouse T cell transformants expressing P2X7, we herein performed CRISPR/Cas9 screening for the molecules responsible for P2X7-mediated PtdSer exposure. In addition to Eros, which is required for the localization of P2X7 to the plasma membrane, this screening identified Xk and Vps13a as essential components for this process. Xk is present at the plasma membrane, and its paralogue, Xkr8, functions as a phospholipid scramblase. Vps13a is a lipid transporter in the cytoplasm. Blue-native polyacrylamide gel electrophoresis indicated that Xk and Vps13a interacted at the membrane. A null mutation in Xk or Vps13a blocked P2X7-mediated PtdSer exposure, the internalization of phosphatidylcholine, and cytolysis. Xk and Vps13a formed a complex in mouse splenic T cells, and Xk was crucial for ATP-induced PtdSer exposure and cytolysis in CD25+CD4+ T cells. XK and VPS13A are responsible for McLeod syndrome and chorea-acanthocytosis, both characterized by a progressive movement disorder and cognitive and behavior changes. Our results suggest that the phospholipid scrambling activity mediated by XK and VPS13A is essential for maintaining homeostasis in the immune and nerve systems.
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5
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Andrei A, Di Renzo MA, Öztürk Y, Meisner A, Daum N, Frank F, Rauch J, Daldal F, Andrade SLA, Koch HG. The CopA2-Type P 1B-Type ATPase CcoI Serves as Central Hub for cbb 3-Type Cytochrome Oxidase Biogenesis. Front Microbiol 2021; 12:712465. [PMID: 34589071 PMCID: PMC8475189 DOI: 10.3389/fmicb.2021.712465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 07/12/2021] [Indexed: 11/13/2022] Open
Abstract
Copper (Cu)-transporting P1B-type ATPases are ubiquitous metal transporters and crucial for maintaining Cu homeostasis in all domains of life. In bacteria, the P1B-type ATPase CopA is required for Cu-detoxification and exports excess Cu(I) in an ATP-dependent reaction from the cytosol into the periplasm. CopA is a member of the CopA1-type ATPase family and has been biochemically and structurally characterized in detail. In contrast, less is known about members of the CopA2-type ATPase family, which are predicted to transport Cu(I) into the periplasm for cuproprotein maturation. One example is CcoI, which is required for the maturation of cbb 3-type cytochrome oxidase (cbb 3-Cox) in different species. Here, we reconstituted purified CcoI of Rhodobacter capsulatus into liposomes and determined Cu transport using solid-supported membrane electrophysiology. The data demonstrate ATP-dependent Cu(I) translocation by CcoI, while no transport is observed in the presence of a non-hydrolysable ATP analog. CcoI contains two cytosolically exposed N-terminal metal binding sites (N-MBSs), which are both important, but not essential for Cu delivery to cbb 3-Cox. CcoI and cbb 3-Cox activity assays in the presence of different Cu concentrations suggest that the glutaredoxin-like N-MBS1 is primarily involved in regulating the ATPase activity of CcoI, while the CopZ-like N-MBS2 is involved in Cu(I) acquisition. The interaction of CcoI with periplasmic Cu chaperones was analyzed by genetically fusing CcoI to the chaperone SenC. The CcoI-SenC fusion protein was fully functional in vivo and sufficient to provide Cu for cbb 3-Cox maturation. In summary, our data demonstrate that CcoI provides the link between the cytosolic and periplasmic Cu chaperone networks during cbb 3-Cox assembly.
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Affiliation(s)
- Andreea Andrei
- Institut für Biochemie und Molekularbiologie, ZBMZ, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.,Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Maria Agostina Di Renzo
- Institute for Biochemistry, Faculty of Chemistry and Pharmacy, Albert-Ludwigs-University Freiburg, Freiburg, Germany.,Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg, Germany.,Faculty of Chemistry and Pharmacy, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Yavuz Öztürk
- Institut für Biochemie und Molekularbiologie, ZBMZ, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Alexandra Meisner
- Institut für Biochemie und Molekularbiologie, ZBMZ, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Noel Daum
- Institut für Biochemie und Molekularbiologie, ZBMZ, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Fabian Frank
- Institute for Biochemistry, Faculty of Chemistry and Pharmacy, Albert-Ludwigs-University Freiburg, Freiburg, Germany
| | - Juna Rauch
- Institut für Biochemie und Molekularbiologie, ZBMZ, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Fevzi Daldal
- Department of Biology, University of Pennsylvania, Philadelphia, PA, United States
| | - Susana L A Andrade
- Institute for Biochemistry, Faculty of Chemistry and Pharmacy, Albert-Ludwigs-University Freiburg, Freiburg, Germany
| | - Hans-Georg Koch
- Institut für Biochemie und Molekularbiologie, ZBMZ, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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6
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Mathioudaki E, Arvaniti K, Muenke C, Drakonaki A, Vranakis I, Koutantou M, Psaroulaki A, Xie H, Tsiotis G. Expression, purification and characterization of the IcmG and IcmK proteins of the type IVB secretion system from Coxiella burnetii. Protein Expr Purif 2021; 186:105905. [PMID: 33989770 DOI: 10.1016/j.pep.2021.105905] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 04/15/2021] [Accepted: 05/06/2021] [Indexed: 10/21/2022]
Abstract
Coxiella burnetii, the causative agent of Q fever, is an intracellular bacterial pathogen. Studies on Coxiella have shown that a type IVB secretion system (T4BSS) contributes to the establishment of the infection by transferring protein molecules. In this report, we focus on two core proteins of the Coxiella T4BSS, namely the IcmG/DotF protein (CBU_1626) and the IcmK/DotH protein (CBU_1628). Here we present a method for the recombinant expression of IcmG and IcmK in E. coli. IcmG was purified by Strep-Tactin affinity chromatography and size exclusion chromatography, while for the purification of IcmK an additional anion exchange chromatography step was introduced. The yields of the purified IcmG and IcmK proteins were 1.2 mg/L and 3 mg/L, respectively. The purified proteins showed predominant band on SDS-PAGE gel of 37 kDa for the IcmG and 40 kDa for the IcmK. Protein folding is confirmed by circular dichroism spectroscopy. The dynamic light scattering experiment indicated that IcmG and IcmK existed in a homogenous form. Further Blue native PAGE indicates the presences of a monomeric form for the IcmK and IcmG. Our work lays the basis for functional exploration and structural determination of IcmG and IcmK proteins of Coxiella's secretion system.
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Affiliation(s)
- Eirini Mathioudaki
- Division of Biochemistry, Department of Chemistry, University of Crete, GR-71003, Voutes, Greece
| | - Katerina Arvaniti
- Division of Biochemistry, Department of Chemistry, University of Crete, GR-71003, Voutes, Greece
| | - Cornelia Muenke
- Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, D-60438, Frankfurt am Main, Germany
| | - Athina Drakonaki
- Division of Biochemistry, Department of Chemistry, University of Crete, GR-71003, Voutes, Greece
| | - Iosif Vranakis
- Department of Clinical Bacteriology, Parasitology, Zoonoses and Geographical Medicine, Medical School, University of Crete, GR-71110, Heraklion, Greece
| | - Myrto Koutantou
- Division of Biochemistry, Department of Chemistry, University of Crete, GR-71003, Voutes, Greece
| | - Anna Psaroulaki
- Department of Clinical Bacteriology, Parasitology, Zoonoses and Geographical Medicine, Medical School, University of Crete, GR-71110, Heraklion, Greece
| | - Hao Xie
- Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, D-60438, Frankfurt am Main, Germany.
| | - Georgios Tsiotis
- Division of Biochemistry, Department of Chemistry, University of Crete, GR-71003, Voutes, Greece.
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7
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Chen V, Bruno AE, Britt LL, Hernandez CC, Gimenez LE, Peisley A, Cone RD, Millhauser GL. Membrane orientation and oligomerization of the melanocortin receptor accessory protein 2. J Biol Chem 2020; 295:16370-16379. [PMID: 32943551 DOI: 10.1074/jbc.ra120.015482] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 09/08/2020] [Indexed: 12/12/2022] Open
Abstract
The melanocortin receptor accessory protein 2 (MRAP2) plays a pivotal role in the regulation of several G protein-coupled receptors that are essential for energy balance and food intake. MRAP2 loss-of-function results in obesity in mammals. MRAP2 and its homolog MRAP1 have an unusual membrane topology and are the only known eukaryotic proteins that thread into the membrane in both orientations. In this study, we demonstrate that the conserved polybasic motif that dictates the membrane topology and dimerization of MRAP1 does not control the membrane orientation and dimerization of MRAP2. We also show that MRAP2 dimerizes through its transmembrane domain and can form higher-order oligomers that arrange MRAP2 monomers in a parallel orientation. Investigating the molecular details of MRAP2 structure is essential for understanding the mechanism by which it regulates G protein-coupled receptors and will aid in elucidating the pathways involved in metabolic dysfunction.
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Affiliation(s)
- Valerie Chen
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California, USA
| | - Antonio E Bruno
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California, USA
| | - Laura L Britt
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California, USA
| | - Ciria C Hernandez
- Life Sciences Institute and Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Luis E Gimenez
- Life Sciences Institute and Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Alys Peisley
- Life Sciences Institute and Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Roger D Cone
- Life Sciences Institute and Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Glenn L Millhauser
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California, USA.
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8
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Shah JS, Renthal R. Antennal Proteome of the Solenopsis invicta (Hymenoptera: Formicidae): Caste Differences in Olfactory Receptors and Chemosensory Support Proteins. JOURNAL OF INSECT SCIENCE (ONLINE) 2020; 20:5937575. [PMID: 33098433 PMCID: PMC7585320 DOI: 10.1093/jisesa/ieaa118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Indexed: 06/11/2023]
Abstract
Little is known about the expression pattern of odorant and pheromone transporters, receptors, and deactivation enzymes in the antennae of ants carrying out different tasks. In order to begin filling in this information gap, we compared the proteomes of the antennae of workers and males of the red fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae). Male ants do not perform any colony work, and their only activity is to leave the nest on a mating flight. Previous studies showed that male ants express fewer types of odorant receptors than workers. Thus, we expected to find large differences between male and worker antennae for expression of receptors, transporters, and deactivators of signaling chemicals. We found that the abundance of receptors was consistent with the expected caste-specific signaling complexity, but the numbers of different antenna-specific transporters and deactivating enzymes in males and workers were similar. It is possible that some of these proteins have antenna-specific functions that are unrelated to chemosensory reception. Alternatively, the similar complexity could be a vestige of ant progenitors that had more behaviorally active males. As the reduced behavior of male ants evolved, the selection process may have favored a complex repertoire of transporters and deactivating enzymes alongside a limited repertoire of odorant receptors.
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Affiliation(s)
- Jaee Shailesh Shah
- Department of Biology, University of Texas at San Antonio, San Antonio, TX
| | - Robert Renthal
- Department of Biology, University of Texas at San Antonio, San Antonio, TX
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Abstract
The integral membrane protein heme A synthase (HAS) catalyzes the biosynthesis of heme A, which is a prerequisite for cellular respiration in a wide range of aerobic organisms. Previous studies have revealed that HAS can form homo-oligomeric complexes, and this oligomerization appears to be evolutionarily conserved among prokaryotes and eukaryotes and is shown to be essential for the biological function of eukaryotic HAS. Despite its importance, little is known about the detailed structural properties of HAS oligomers. Here, we aimed to address this critical issue by analyzing the oligomeric state of HAS from Aquifex aeolicus (AaHAS) using a combination of techniques, including size exclusion chromatography coupled with multiangle light scattering (SEC-MALS), cross-linking, laser-induced liquid bead ion desorption mass spectrometry (LILBID-MS), and single-particle electron cryomicroscopy (cryo-EM). Our results show that HAS forms a thermostable trimeric complex. A cryo-EM density map provides information on the oligomerization interface of the AaHAS trimer. These results provide structural insights into HAS multimerization and expand our knowledge of this important enzyme.IMPORTANCE Heme A is a vital redox cofactor unique for the terminal cytochrome c oxidase in mitochondria and many microorganisms. It plays a key role in oxygen reduction by serving as an electron carrier and as the oxygen-binding site. Heme A is synthesized from heme O by an integral membrane protein, heme A synthase (HAS). Defects in HAS impair cellular respiration and have been linked to various human diseases, e.g., fatal infantile hypertrophic cardiomyopathy and Leigh syndrome. HAS exists as a stable oligomeric complex, and studies have shown that oligomerization of eukaryotic HAS is necessary for its proper function. However, the molecular architecture of the HAS oligomeric complex has remained uncharacterized. The present study shows that HAS forms trimers and reveals how the oligomeric arrangement contributes to the complex stability and flexibility, enabling HAS to perform its catalytic function effectively. This work provides the basic understanding for future studies on heme A biosynthesis.
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10
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Daniels MJ, Jagielnicki M, Yeager M. Structure/Function Analysis of human ZnT8 (SLC30A8): A Diabetes Risk Factor and Zinc Transporter. Curr Res Struct Biol 2020; 2:144-155. [PMID: 34235474 PMCID: PMC8244513 DOI: 10.1016/j.crstbi.2020.06.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 06/15/2020] [Accepted: 06/22/2020] [Indexed: 12/17/2022] Open
Abstract
The human zinc transporter ZnT8 (SLC30A8) is expressed primarily in pancreatic β-cells and plays a key function in maintaining the concentration of blood glucose through its role in insulin storage, maturation and secretion. ZnT8 is an autoantigen for Type 1 diabetes (T1D) and is associated with Type 2 diabetes (T2D) through its risk allele that encodes a major non-synonymous single nucleotide polymorphism (SNP) at Arg325. Loss of function mutations improve insulin secretion and are protective against diabetes. Despite its role in diabetes and concomitant potential as a drug target, little is known about the structure or mechanism of ZnT8. To this end, we expressed ZnT8 in Pichia pastoris yeast and Sf9 insect cells. Guided by a rational screen of 96 detergents, we developed a method to solubilize and purify recombinant ZnT8. An in vivo transport assay in Pichia and a liposome-based uptake assay for insect-cell derived ZnT8 showed that the protein is functionally active in both systems. No significant difference in activity was observed between full-length ZnT8 (ZnT8A) and the amino-terminally truncated ZnT8B isoform. A fluorescence-based in vitro transport assay using proteoliposomes indicated that human ZnT8 functions as a Zn2+/H+ antiporter. We also purified E. coli-expressed amino- and carboxy-terminal cytoplasmic domains of ZnT8A. Circular dichroism spectrometry suggested that the amino-terminal domain contains predominantly α-helical structure, and indicated that the carboxy-terminal domain has a mixed α/β structure. Negative-stain electron microscopy and single-particle image analysis yielded a density map of ZnT8B at 20 Å resolution, which revealed that ZnT8 forms a dimer in detergent micelles. Two prominent lobes are ascribed to the transmembrane domains, and the molecular envelope recapitulates that of the bacterial zinc transporter YiiP. These results provide a foundation for higher resolution structural studies and screening experiments to identify compounds that modulate ZnT8 activity.
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Affiliation(s)
- Mark J. Daniels
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Maciej Jagielnicki
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
- Department of Biochemistry, University of Toronto, Toronto, ON, M5G 1M1, Canada
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
- Department of Medicine, Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, VA, 22908, USA
- Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
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11
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Díaz-García C, Hornos F, Giudici AM, Cámara-Artigas A, Luque-Ortega JR, Arbe A, Rizzuti B, Alfonso C, Forwood JK, Iovanna JL, Gómez J, Prieto M, Coutinho A, Neira JL. Human importin α3 and its N-terminal truncated form, without the importin-β-binding domain, are oligomeric species with a low conformational stability in solution. Biochim Biophys Acta Gen Subj 2020; 1864:129609. [PMID: 32234409 DOI: 10.1016/j.bbagen.2020.129609] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 03/13/2020] [Accepted: 03/26/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND Eukaryotic cells have a continuous transit of macromolecules between the cytoplasm and the nucleus. Several carrier proteins are involved in this transport. One of them is importin α, which must form a complex with importin β to accomplish its function, by domain-swapping its 60-residue-long N terminus. There are several human isoforms of importin α; among them, importin α3 has a particularly high flexibility. METHODS We studied the conformational stability of intact importin α3 (Impα3) and its truncated form, where the 64-residue-long, N-terminal importin-β-binding domain (IBB) has been removed (ΔImpα3), in a wide pH range, with several spectroscopic, biophysical, biochemical methods and with molecular dynamics (MD). RESULTS Both species acquired native-like structure between pH 7 and 10.0, where Impα3 was a dimer (with an apparent self-association constant of ~10 μM) and ΔImpα3 had a higher tendency to self-associate than the intact species. The acquisition of secondary, tertiary and quaternary structure, and the burial of hydrophobic patches, occurred concomitantly. Both proteins unfolded irreversibly at physiological pH, by using either temperature or chemical denaturants, through several partially folded intermediates. The MD simulations support the presence of these intermediates. CONCLUSIONS The thermal stability of Impα3 at physiological pH was very low, but was higher than that of ΔImpα3. Both proteins were stable in a narrow pH range, and they unfolded at physiological pH populating several intermediate species. GENERAL SIGNIFICANCE The low conformational stability explains the flexibility of Impα3, which is needed to carry out its recognition of complex cargo sequences.
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Affiliation(s)
- Clara Díaz-García
- iBB- Institute for Bioengineering and Bioscience, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisboa, Portugal
| | - Felipe Hornos
- IDIBE, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain
| | | | - Ana Cámara-Artigas
- Departamento de Química y Física, Research Center CIAIMBITAL, Universidad de Almería- ceiA3, 04120 Almería, Spain
| | - Juan Román Luque-Ortega
- Centro de Investigaciones Biológicas Margarita Salas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Arantxa Arbe
- Centro de Física de Materiales (CFM) (CSIC-UPV/EHU), Materials Physics Center (MPC), 20018 San Sebastián, Spain
| | - Bruno Rizzuti
- CNR-NANOTEC, Licryl-UOS Cosenza and CEMIF.Cal, Department of Physics, University of Calabria, Via P. Bucci, Cubo 31 C, 87036 Arcavacata di Rende, Cosenza, Italy
| | - Carlos Alfonso
- Centro de Investigaciones Biológicas Margarita Salas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Jade K Forwood
- School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia
| | - Juan L Iovanna
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM U1068, CNRS UMR 7258, Aix-Marseille Université and Institut Paoli-Calmettes, Parc Scientifique et Technologique de Luminy, 163 Avenue de Luminy, 13288 Marseille, France
| | - Javier Gómez
- IDIBE, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain
| | - Manuel Prieto
- iBB- Institute for Bioengineering and Bioscience, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisboa, Portugal
| | - Ana Coutinho
- iBB- Institute for Bioengineering and Bioscience, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisboa, Portugal; Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1649-004 Lisboa, Portugal
| | - José L Neira
- IDIBE, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain; Instituto de Biocomputación y Física de Sistemas Complejos, Joint Units IQFR-CSIC-BIFI, and GBsC-CSIC-BIFI, Universidad de Zaragoza, 50009 Zaragoza, Spain.
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12
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Gupta A, Bokhari AAB, Pillai AD, Crater AK, Gezelle J, Saggu G, Nasamu AS, Ganesan SM, Niles JC, Desai SA. Complex nutrient channel phenotypes despite Mendelian inheritance in a Plasmodium falciparum genetic cross. PLoS Pathog 2020; 16:e1008363. [PMID: 32069335 PMCID: PMC7048409 DOI: 10.1371/journal.ppat.1008363] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 02/28/2020] [Accepted: 01/28/2020] [Indexed: 12/30/2022] Open
Abstract
Malaria parasites activate a broad-selectivity ion channel on their host erythrocyte membrane to obtain essential nutrients from the bloodstream. This conserved channel, known as the plasmodial surface anion channel (PSAC), has been linked to parasite clag3 genes in P. falciparum, but epigenetic switching between the two copies of this gene hinders clear understanding of how the encoded protein determines PSAC activity. Here, we used linkage analysis in a P. falciparum cross where one parent carries a single clag3 gene to overcome the effects of switching and confirm a primary role of the clag3 product with high confidence. Despite Mendelian inheritance, CLAG3 conditional knockdown revealed remarkably preserved nutrient and solute uptake. Even more surprisingly, transport remained sensitive to a CLAG3 isoform-specific inhibitor despite quantitative knockdown, indicating that low doses of the CLAG3 transgene are sufficient to confer block. We then produced a complete CLAG3 knockout line and found it exhibits an incomplete loss of transport activity, in contrast to rhoph2 and rhoph3, two PSAC-associated genes that cannot be disrupted because nutrient uptake is abolished in their absence. Although the CLAG3 knockout did not incur a fitness cost under standard nutrient-rich culture conditions, this parasite could not be propagated in a modified medium that more closely resembles human plasma. These studies implicate oligomerization of CLAG paralogs encoded by various chromosomes in channel formation. They also reveal that CLAG3 is dispensable under standard in vitro conditions but required for propagation under physiological conditions.
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Affiliation(s)
- Ankit Gupta
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Abdullah A. B. Bokhari
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Ajay D. Pillai
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Anna K. Crater
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Jeanine Gezelle
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Gagandeep Saggu
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Armiyaw S. Nasamu
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Suresh M. Ganesan
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Jacquin C. Niles
- Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Sanjay A. Desai
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
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13
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Antibodies binding the head domain of P2X4 inhibit channel function and reverse neuropathic pain. Pain 2019; 160:1989-2003. [DOI: 10.1097/j.pain.0000000000001587] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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14
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Idso MN, Baxter NR, Narayanan S, Chang E, Fisher J, Chmelka BF, Han S. Proteorhodopsin Function Is Primarily Mediated by Oligomerization in Different Micellar Surfactant Solutions. J Phys Chem B 2019; 123:4180-4192. [DOI: 10.1021/acs.jpcb.9b00922] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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15
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Kumagai K, Elwell CA, Ando S, Engel JN, Hanada K. Both the N- and C- terminal regions of the Chlamydial inclusion protein D (IncD) are required for interaction with the pleckstrin homology domain of the ceramide transport protein CERT. Biochem Biophys Res Commun 2018; 505:1070-1076. [PMID: 30314703 DOI: 10.1016/j.bbrc.2018.09.168] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 09/26/2018] [Indexed: 11/24/2022]
Abstract
Chlamydia trachomatis is an obligate intracellular bacterium that replicates within a membranous compartment, the inclusion, in host cells. Its intracellular life cycle requires host sphingolipids, which are in part acquired through the ER-Golgi localized ceramide transport protein (CERT). The Chlamydia-encoded inclusion membrane protein IncD is composed of two closely linked long hydrophobic domains with their N- and C-termini exposed to the host cytosol. IncD binds directly to the pleckstrin homology (PH) domain of CERT, likely redirecting ceramide to the inclusion. The precise regions of IncD required for this interaction have not been delineated. Using co-transfection studies together with phylogenetic studies, we demonstrate that both the IncD N- and C-terminal regions are required for binding to the CERT PH domain and define key interaction residues. Native gel electrophoresis analysis demonstrates that the transmembrane region of IncD forms SDS-resistant but dithiothreitol-sensitive homodimers, which in turn can assemble to form higher order oligomers through additional N- and C-terminal domain contacts. IncD oligomerization may facilitate high affinity binding to CERT, allowing C. trachomatis to efficiently redirect host ceramide to the inclusion.
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Affiliation(s)
- Keigo Kumagai
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo, 162-8640, Japan.
| | - Cherilyn A Elwell
- Department of Medicine, University of California, San Francisco, CA, USA
| | - Shuji Ando
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo, 162-8640, Japan
| | - Joanne N Engel
- Department of Medicine, University of California, San Francisco, CA, USA; Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
| | - Kentaro Hanada
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo, 162-8640, Japan.
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CLAG3 Self-Associates in Malaria Parasites and Quantitatively Determines Nutrient Uptake Channels at the Host Membrane. mBio 2018; 9:mBio.02293-17. [PMID: 29739907 PMCID: PMC5941077 DOI: 10.1128/mbio.02293-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Malaria parasites increase host erythrocyte permeability to ions and nutrients via a broad-selectivity channel known as the plasmodial surface anion channel (PSAC), linked to parasite-encoded CLAG3 and two associated proteins. These proteins lack the multiple transmembrane domains typically present in channel-forming proteins, raising doubts about their precise roles. Using the virulent human Plasmodium falciparum parasite, we report that CLAG3 undergoes self-association and that this protein’s expression determines channel phenotype quantitatively. We overcame epigenetic silencing of clag3 paralogs and engineered parasites that express two CLAG3 isoforms simultaneously. Stoichiometric expression of these isoforms yielded intermediate channel phenotypes, in agreement with observed trafficking of both proteins to the host membrane. Coimmunoprecipitation and surface labeling revealed formation of CLAG3 oligomers. In vitro selections applied to these transfectant lines yielded distinct mutants with correlated changes in channel activity. These findings support involvement of the identified oligomers in PSAC formation and parasite nutrient acquisition. Malaria parasites are globally important pathogens that evade host immunity by replicating within circulating erythrocytes. To facilitate intracellular growth, these parasites increase erythrocyte nutrient uptake through an unusual ion channel. The parasite CLAG3 protein is a key determinant of this channel, but its lack of homology to known ion channels has raised questions about possible mechanisms. Using a new method that allows simultaneous expression of two different CLAG3 proteins, we identify self-association of CLAG3. The two expressed isoforms faithfully traffic to and insert in the host membrane, while remaining associated with two unrelated parasite proteins. Both the channel phenotypes and molecular changes produced upon selections with a highly specific channel inhibitor are consistent with a multiprotein complex that forms the nutrient pore. These studies support direct involvement of the CLAG3 protein in channel formation and are relevant to antimalarial drug discovery projects targeting parasite nutrient acquisition.
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Abstract
Transmembrane protein 16F (TMEM16F) is a Ca2+-dependent phospholipid scramblase that translocates phospholipids bidirectionally between the leaflets of the plasma membrane. Phospholipid scrambling of TMEM16F causes exposure of phosphatidylserine in activated platelets to induce blood clotting and in differentiated osteoblasts to promote bone mineralization. Despite the importance of TMEM16F-mediated phospholipid scrambling in various biological reactions, the fundamental features of the scrambling reaction remain elusive due to technical difficulties in the preparation of a platform for assaying scramblase activity in vitro. Here, we established a method to express and purify mouse TMEM16F as a dimeric molecule by constructing a stable cell line and developed a microarray containing membrane bilayers with asymmetrically distributed phospholipids as a platform for single-molecule scramblase assays. The purified TMEM16F was integrated into the microarray, and monitoring of phospholipid translocation showed that a single TMEM16F molecule transported phospholipids nonspecifically between the membrane bilayers in a Ca2+-dependent manner. Thermodynamic analysis of the reaction indicated that TMEM16F transported 4.5 × 104 lipids per second at 25 °C, with an activation free energy of 47 kJ/mol. These biophysical features were similar to those observed with channels, which transport substrates by facilitating diffusion, and supported the stepping-stone model for the TMEM16F phospholipid scramblase.
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18
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Surya W, Li Y, Torres J. Structural model of the SARS coronavirus E channel in LMPG micelles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1309-1317. [PMID: 29474890 PMCID: PMC7094280 DOI: 10.1016/j.bbamem.2018.02.017] [Citation(s) in RCA: 113] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 02/14/2018] [Accepted: 02/16/2018] [Indexed: 01/27/2023]
Abstract
Coronaviruses (CoV) cause common colds in humans, but are also responsible for the recent Severe Acute, and Middle East, respiratory syndromes (SARS and MERS, respectively). A promising approach for prevention are live attenuated vaccines (LAVs), some of which target the envelope (E) protein, which is a small membrane protein that forms ion channels. Unfortunately, detailed structural information is still limited for SARS-CoV E, and non-existent for other CoV E proteins. Herein, we report a structural model of a SARS-CoV E construct in LMPG micelles with, for the first time, unequivocal intermolecular NOEs. The model corresponding to the detergent-embedded region is consistent with previously obtained orientational restraints obtained in lipid bilayers and in vivo escape mutants. The C-terminal domain is mostly α-helical, and extramembrane intermolecular NOEs suggest interactions that may affect the TM channel conformation.
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Affiliation(s)
- Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Yan Li
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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19
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Segawa K, Kurata S, Nagata S. The CDC50A extracellular domain is required for forming a functional complex with and chaperoning phospholipid flippases to the plasma membrane. J Biol Chem 2017; 293:2172-2182. [PMID: 29276178 DOI: 10.1074/jbc.ra117.000289] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 12/21/2017] [Indexed: 02/04/2023] Open
Abstract
Flippases are enzymes that translocate phosphatidylserine (PtdSer) and phosphatidylethanolamine (PtdEtn) from the outer to the inner leaflet in the lipid bilayer of the plasma membrane, leading to the asymmetric distribution of aminophospholipids in the membrane. One mammalian phospholipid flippase at the plasma membrane is ATP11C, a type IV P-type ATPase (P4-ATPase) that forms a heterocomplex with the transmembrane protein CDC50A. However, the structural features in CDC50A that support the function of ATP11C and other P4-ATPases have not been characterized. Here, using error-prone PCR-mediated mutagenesis of human CDC50A cDNA followed by functional screening and deep sequencing, we identified 14 amino acid residues that affect ATP11C's flippase activity. These residues were all located in CDC50A's extracellular domain and were evolutionarily well-conserved. Most of the mutations decreased CDC50A's ability to chaperone ATP11C and other P4-ATPases to their destinations. The CDC50A mutants failed to form a stable complex with ATP11C and could not induce ATP11C's PtdSer-dependent ATPase activity. Notably, one mutant variant could form a stable complex with ATP11C and transfer ATP11C to the plasma membrane, yet the ATP11C complexed with this CDC50A variant had very weak or little PtdSer- or PtdEtn-dependent ATPase activity. These results indicated that the extracellular domain of CDC50A has important roles both in CDC50A's ability to chaperone ATP11C to the plasma membrane and in inducing ATP11C's ATP hydrolysis-coupled flippase activity.
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Affiliation(s)
- Katsumori Segawa
- From the Laboratory of Biochemistry and Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
| | - Sachiko Kurata
- From the Laboratory of Biochemistry and Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
| | - Shigekazu Nagata
- From the Laboratory of Biochemistry and Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
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Identification of multienzymatic complexes in the Clonostachys byssicola secretomes produced in response to different lignocellulosic carbon sources. J Biotechnol 2017; 254:51-58. [PMID: 28610997 DOI: 10.1016/j.jbiotec.2017.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 05/26/2017] [Accepted: 06/05/2017] [Indexed: 01/29/2023]
Abstract
Multienzymatic complexes with plant lignocellulose-degrading activities have recently been identified in filamentous fungi secretomes. Such complexes have potential biotechnological applications in the degradation of agro-industrial residues. Fungal species from the Clonostachys genus have been intensively investigated as biocontrol agents; however so far their use as producers of lignocellulose-degrading enzymes has not been extensively explored. Secretomes of Clonostachys byssicola following growth on different carbon sources (passion fruit peel, soybean hulls, cotton gin trash, banana stalk, sugarcane bagasse, orange peel, and a composition of soybean hulls: cotton gin trash:orange peel) were subjected to enzymatic assays. Remarkable differences were observed among the samples, especially regarding levels of mannanase and pectinase activities. Secretomes were then subjected to Blue Native PAGE in order to resolve putative protein complexes which subsequently had their composition revealed by trypsin digestion followed by LC-MS/MS analysis. The protein bands (named I, II, III and IV) were shown to be composed by holocellulolytic enzymes, mainly cellulases and xylanases as well as proteins involved in biocontrol processes, such as chitinases and proteases. The high diversity of proteins found in these multicatalytic assemblies confirms C. byssicola as a novel source of plant biomass-degrading enzymes.
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Structure and elevator mechanism of the Na +-citrate transporter CitS. Curr Opin Struct Biol 2016; 45:1-9. [PMID: 27776291 DOI: 10.1016/j.sbi.2016.10.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 10/04/2016] [Accepted: 10/05/2016] [Indexed: 10/20/2022]
Abstract
The recently determined crystal structure of the bacterial Na+-citrate symporter CitS provides unexpected structural and mechanistic insights. The protein has a fold that has not been seen in other proteins, but the oligomeric state, domain organization and proposed transport mechanism strongly resemble those of the sodium-dicarboxylate symporter vcINDY, and the putative exporters YdaH and MtrF, thus hinting at convergence in structure and function. CitS and the related proteins are predicted to translocate their substrates by an elevator-like mechanism, in which a compact transport domain slides up and down through the membrane while the dimerization domain is stably anchored. Here we review the large body of available biochemical data on CitS in the light of the new crystal structure. We show that the biochemical data are fully consistent with the proposed elevator mechanism, but also demonstrate that the current structural data cannot explain how strict coupling of citrate and Na+ transport is achieved. We propose a testable model for the coupling mechanism.
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22
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Xkr8 phospholipid scrambling complex in apoptotic phosphatidylserine exposure. Proc Natl Acad Sci U S A 2016; 113:9509-14. [PMID: 27503893 DOI: 10.1073/pnas.1610403113] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Xk-related protein (Xkr) 8, a protein carrying 10 transmembrane regions, is essential for scrambling phospholipids during apoptosis. Here, we found Xkr8 as a complex with basigin (BSG) or neuroplastin (NPTN), type I membrane proteins in the Ig superfamily. In BSG(-/-)NPTN(-/-) cells, Xkr8 localized intracellularly, and the apoptosis stimuli failed to expose phosphatidylserine, indicating that BSG and NPTN chaperone Xkr8 to the plasma membrane to execute its scrambling activity. Mutational analyses of BSG showed that the atypical glutamic acid in the transmembrane region is required for BSG's association with Xkr8. In cells exposed to apoptotic signals, Xkr8 was cleaved at the C terminus and the Xkr8/BSG complex formed a higher-order complex, likely to be a heterotetramer consisting of two molecules of Xkr8 and two molecules of BSG or NPTN, suggesting that this cleavage causes the formation of a larger complex of Xkr8-BSG/NPTN for phospholipid scrambling.
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23
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Kao WC, Kleinschroth T, Nitschke W, Baymann F, Neehaul Y, Hellwig P, Richers S, Vonck J, Bott M, Hunte C. The obligate respiratory supercomplex from Actinobacteria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1705-14. [PMID: 27472998 DOI: 10.1016/j.bbabio.2016.07.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 06/27/2016] [Accepted: 07/23/2016] [Indexed: 10/21/2022]
Abstract
Actinobacteria are closely linked to human life as industrial producers of bioactive molecules and as human pathogens. Respiratory cytochrome bcc complex and cytochrome aa3 oxidase are key components of their aerobic energy metabolism. They form a supercomplex in the actinobacterial species Corynebacterium glutamicum. With comprehensive bioinformatics and phylogenetic analysis we show that genes for cyt bcc-aa3 supercomplex are characteristic for Actinobacteria (Actinobacteria and Acidimicrobiia, except the anaerobic orders Actinomycetales and Bifidobacteriales). An obligatory supercomplex is likely, due to the lack of genes encoding alternative electron transfer partners such as mono-heme cyt c. Instead, subunit QcrC of bcc complex, here classified as short di-heme cyt c, will provide the exclusive electron transfer link between the complexes as in C. glutamicum. Purified to high homogeneity, the C. glutamicum bcc-aa3 supercomplex contained all subunits and cofactors as analyzed by SDS-PAGE, BN-PAGE, absorption and EPR spectroscopy. Highly uniform supercomplex particles in electron microscopy analysis support a distinct structural composition. The supercomplex possesses a dimeric stoichiometry with a ratio of a-type, b-type and c-type hemes close to 1:1:1. Redox titrations revealed a low potential bcc complex (Em(ISP)=+160mV, Em(bL)=-291mV, Em(bH)=-163mV, Em(cc)=+100mV) fined-tuned for oxidation of menaquinol and a mixed potential aa3 oxidase (Em(CuA)=+150mV, Em(a/a3)=+143/+317mV) mediating between low and high redox potential to accomplish dioxygen reduction. The generated molecular model supports a stable assembled supercomplex with defined architecture which permits energetically efficient coupling of menaquinol oxidation and dioxygen reduction in one supramolecular entity.
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Affiliation(s)
- Wei-Chun Kao
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, BIOSS Centre for Biological Signalling Studies, 79104 Freiburg, Germany
| | - Thomas Kleinschroth
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, BIOSS Centre for Biological Signalling Studies, 79104 Freiburg, Germany
| | - Wolfgang Nitschke
- Laboratoire de Bioénergétique et Ingénierie des Protéines UMR 7281 CNRS/Aix Marseille Univ, FR3479, 13009 Marseille, France
| | - Frauke Baymann
- Laboratoire de Bioénergétique et Ingénierie des Protéines UMR 7281 CNRS/Aix Marseille Univ, FR3479, 13009 Marseille, France
| | - Yashvin Neehaul
- Laboratoire de bioélectrochimie et spectroscopie, UMR 7140, Chimie de la matière complexe, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France
| | - Petra Hellwig
- Laboratoire de bioélectrochimie et spectroscopie, UMR 7140, Chimie de la matière complexe, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France
| | - Sebastian Richers
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Janet Vonck
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Michael Bott
- Institute of Bio- and Geosciences, IBG-1: Biotechnology, Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Carola Hunte
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, BIOSS Centre for Biological Signalling Studies, 79104 Freiburg, Germany.
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Frixel S, Lotz-Havla AS, Kern S, Kaltenborn E, Wittmann T, Gersting SW, Muntau AC, Zarbock R, Griese M. Homooligomerization of ABCA3 and its functional significance. Int J Mol Med 2016; 38:558-66. [PMID: 27352740 DOI: 10.3892/ijmm.2016.2650] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 05/11/2016] [Indexed: 11/06/2022] Open
Abstract
ABCA3 is a surfactant lipid transporter in the limiting membrane of lamellar bodies in alveolar type II cells. Mutations in the ATP-binding cassette, sub-family A (ABC1), member 3 (ABCA3) gene cause respiratory distress syndrome in newborns, and chronic interstitial lung disease in children and adults. ABCA3 belongs to the class of full ABC transporters, which are supposed to be functional in their monomeric forms. Although other family members e.g., ABCA1 and ABCC7 have been shown to function as oligomers, the oligomerization state of ABCA3 is unknown. In the present study, the oligomerization of ABCA3 was investigated in cell lysates and crude membrane preparations from transiently and stably transfected 293 cells using blue native PAGE (BN-PAGE), gel filtration and co-immunoprecipitation. Additionally, homooligomerization was examined in vivo in cells using bioluminescence resonance energy transfer (BRET). Using BN-PAGE and gel filtration, we demonstrate that non-denatured ABCA3 exists in different oligomeric forms, with monomers (45%) and tetramers (30%) being the most abundant forms. Furthermore, we also show the existence of 20% dimers and 5% trimers. BRET analyses verified intermolecular interactions in vivo. Our results also demonstrated that the arrest of ABCA3 in the endoplasmic reticulum (ER), either through drug treatment or induced by mutations in ABCA3, inhibited the propensity of the protein to form dimers. Based on our results, we suggest that transporter oligomerization is crucial for ABCA3 function and that a disruption of oligomerization due to mutations represents a novel pathomechanism in ABCA3-associated lung disease.
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Affiliation(s)
- Sabrina Frixel
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Amelie S Lotz-Havla
- Department of Molecular Pediatrics, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Sunčana Kern
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Eva Kaltenborn
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Thomas Wittmann
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Søren W Gersting
- Department of Molecular Pediatrics, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Ania C Muntau
- University Children's Hospital, University Medical Center Hamburg-Eppendorf, D-20246 Hamburg, Germany
| | - Ralf Zarbock
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Matthias Griese
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
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25
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Ishihara K, Suzuki J, Nagata S. Role of Ca(2+) in the Stability and Function of TMEM16F and 16K. Biochemistry 2016; 55:3180-8. [PMID: 27227820 DOI: 10.1021/acs.biochem.6b00176] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
There are 10 transmembrane protein (TMEM) 16-family proteins in humans and mice. Among them, TMEM16F acts as a Ca(2+)-dependent phospholipid scramblase at the plasma membrane. However, how Ca(2+) activates TMEM16F's phospholipid-scramblase activity has not been elucidated. Here we found that in the presence of Ca(2+), TMEM16K (whose function is unknown) directly binds Ca(2+) to form a stable complex that can be detected by blue-native polyacrylamide gel electrophoresis. In the absence of Ca(2+), TMEM16K and TMEM16F aggregated, suggesting that their structure is stabilized by Ca(2+). Comprehensive mutagenesis of acidic residues in TMEM16K's cytoplasmic and transmembrane regions identified five residues that are critical for binding Ca(2+). These residues were well conserved between TMEM16F and 16K, and point mutations of these residues in TMEM16F reduced its ability to support Ca(2+)-dependent phospholipid scrambling. Our results suggest that Ca(2+) binds TMEM16F directly and induces conformational changes that support its stability and function.
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Affiliation(s)
- Kenji Ishihara
- Biochemistry & Immunology, Immunology Frontier Research Center, Osaka University , 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Jun Suzuki
- Biochemistry & Immunology, Immunology Frontier Research Center, Osaka University , 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Shigekazu Nagata
- Biochemistry & Immunology, Immunology Frontier Research Center, Osaka University , 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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26
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Fragment Screening of Human Aquaporin 1. Int J Mol Sci 2016; 17:449. [PMID: 27023529 PMCID: PMC4848905 DOI: 10.3390/ijms17040449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 03/14/2016] [Accepted: 03/18/2016] [Indexed: 11/17/2022] Open
Abstract
Aquaporins (AQPs) are membrane proteins that enable water transport across cellular plasma membranes in response to osmotic gradients. Phenotypic analyses have revealed important physiological roles for AQPs, and the potential for AQP water channel modulators in various disease states has been proposed. For example, AQP1 is overexpressed in tumor microvessels, and this correlates with higher metastatic potential and aggressiveness of the malignancy. Chemical modulators would help in identifying the precise contribution of water channel activity in these disease states. These inhibitors would also be important therapeutically, e.g., in anti-cancer treatment. This perceived importance contrasts with the lack of success of high-throughput screens (HTS) to identify effective and specific inhibitors of aquaporins. In this paper, we have screened a library of 1500 "fragments", i.e., smaller than molecules used in HTS, against human aquaporin (hAQP1) using a thermal shift assay and surface plasmon resonance. Although these fragments may not inhibit their protein target, they bound to and stabilized hAQP1 (sub mM binding affinities (KD), with an temperature of aggregation shift ΔTagg of +4 to +50 °C) in a concentration-dependent fashion. Chemically expanded versions of these fragments should follow the determination of their binding site on the aquaporin surface.
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27
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Bischof LF, Friedrich C, Harms A, Søgaard-Andersen L, van der Does C. The Type IV Pilus Assembly ATPase PilB of Myxococcus xanthus Interacts with the Inner Membrane Platform Protein PilC and the Nucleotide-binding Protein PilM. J Biol Chem 2016; 291:6946-57. [PMID: 26851283 DOI: 10.1074/jbc.m115.701284] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Indexed: 01/01/2023] Open
Abstract
Type IV pili (T4P) are ubiquitous bacterial cell surface structures, involved in processes such as twitching motility, biofilm formation, bacteriophage infection, surface attachment, virulence, and natural transformation. T4P are assembled by machinery that can be divided into the outer membrane pore complex, the alignment complex that connects components in the inner and outer membrane, and the motor complex in the inner membrane and cytoplasm. Here, we characterize the inner membrane platform protein PilC, the cytosolic assembly ATPase PilB of the motor complex, and the cytosolic nucleotide-binding protein PilM of the alignment complex of the T4P machinery ofMyxococcus xanthus PilC was purified as a dimer and reconstituted into liposomes. PilB was isolated as a monomer and bound ATP in a non-cooperative manner, but PilB fused to Hcp1 ofPseudomonas aeruginosaformed a hexamer and bound ATP in a cooperative manner. Hexameric but not monomeric PilB bound to PilC reconstituted in liposomes, and this binding stimulated PilB ATPase activity. PilM could only be purified when it was stabilized by a fusion with a peptide corresponding to the first 16 amino acids of PilN, supporting an interaction between PilM and PilN(1-16). PilM-N(1-16) was isolated as a monomer that bound but did not hydrolyze ATP. PilM interacted directly with PilB, but only with PilC in the presence of PilB, suggesting an indirect interaction. We propose that PilB interacts with PilC and with PilM, thus establishing the connection between the alignment and the motor complex.
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Affiliation(s)
- Lisa Franziska Bischof
- From the Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg and the Institute of Biology II, Molecular Biology of Archaea, University of Freiburg, D-79104 Freiburg, Germany
| | - Carmen Friedrich
- From the Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg and
| | - Andrea Harms
- From the Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg and
| | - Lotte Søgaard-Andersen
- From the Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg and
| | - Chris van der Does
- From the Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg and the Institute of Biology II, Molecular Biology of Archaea, University of Freiburg, D-79104 Freiburg, Germany
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28
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Molina ML, Giudici AM, Poveda JA, Fernández-Ballester G, Montoya E, Renart ML, Fernández AM, Encinar JA, Riquelme G, Morales A, González-Ros JM. Competing Lipid-Protein and Protein-Protein Interactions Determine Clustering and Gating Patterns in the Potassium Channel from Streptomyces lividans (KcsA). J Biol Chem 2015; 290:25745-55. [PMID: 26336105 DOI: 10.1074/jbc.m115.669598] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Indexed: 11/06/2022] Open
Abstract
There is increasing evidence to support the notion that membrane proteins, instead of being isolated components floating in a fluid lipid environment, can be assembled into supramolecular complexes that take part in a variety of cooperative cellular functions. The interplay between lipid-protein and protein-protein interactions is expected to be a determinant factor in the assembly and dynamics of such membrane complexes. Here we report on a role of anionic phospholipids in determining the extent of clustering of KcsA, a model potassium channel. Assembly/disassembly of channel clusters occurs, at least partly, as a consequence of competing lipid-protein and protein-protein interactions at nonannular lipid binding sites on the channel surface and brings about profound changes in the gating properties of the channel. Our results suggest that these latter effects of anionic lipids are mediated via the Trp(67)-Glu(71)-Asp(80) inactivation triad within the channel structure and its bearing on the selectivity filter.
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Affiliation(s)
- M Luisa Molina
- From the Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain
| | - A Marcela Giudici
- From the Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain
| | - José A Poveda
- From the Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain
| | | | - Estefanía Montoya
- From the Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain
| | - M Lourdes Renart
- From the Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain
| | - Asia M Fernández
- From the Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain
| | - José A Encinar
- From the Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain
| | - Gloria Riquelme
- the Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, 1027 Santiago, Chile, and
| | - Andrés Morales
- the Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, 03080 Alicante, Spain
| | - José M González-Ros
- From the Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain,
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29
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Rasmussen T, Rasmussen A, Singh S, Galbiati H, Edwards MD, Miller S, Booth IR. Properties of the Mechanosensitive Channel MscS Pore Revealed by Tryptophan Scanning Mutagenesis. Biochemistry 2015; 54:4519-30. [PMID: 26126964 PMCID: PMC4519979 DOI: 10.1021/acs.biochem.5b00294] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Bacterial mechanosensitive channels
gate when the transmembrane
turgor rises to levels that compromise the structural integrity of
the cell wall. Gating creates a transient large diameter pore that
allows hydrated solutes to pass from the cytoplasm at rates close
to those of diffusion. In the closed conformation, the channel limits
transmembrane solute movement, even that of protons. In the MscS crystal
structure (Protein Data Bank entry 2oau), a narrow, hydrophobic opening is visible
in the crystal structure, and it has been proposed that a vapor lock
created by the hydrophobic seals, L105 and L109, is the barrier to
water and ions. Tryptophan scanning mutagenesis has proven to be a
highly valuable tool for the analysis of channel structure. Here Trp
residues were introduced along the pore-forming TM3a helix and in
selected other parts of the protein. Mutants were investigated for
their expression, stability, and activity and as fluorescent probes
of the physical properties along the length of the pore. Most Trp
mutants were expressed at levels similar to that of the parent (MscS
YFF) and were stable as heptamers in detergent in the presence and
absence of urea. Fluorescence data suggest a long hydrophobic region
with low accessibility to aqueous solvents, extending from L105/L109
to G90. Steady-state fluorescence anisotropy data are consistent with
significant homo-Förster resonance energy transfer between
tryptophan residues from different subunits within the narrow pore.
The data provide new insights into MscS structure and gating.
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Affiliation(s)
- Tim Rasmussen
- †School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Akiko Rasmussen
- †School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Shivani Singh
- †School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Heloisa Galbiati
- †School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Michelle D Edwards
- †School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Samantha Miller
- †School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Ian R Booth
- †School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom.,‡Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
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30
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Sverzhinsky A, Qian S, Yang L, Allaire M, Moraes I, Ma D, Chung JW, Zoonens M, Popot JL, Coulton JW. Amphipol-Trapped ExbB–ExbD Membrane Protein Complex from Escherichia coli: A Biochemical and Structural Case Study. J Membr Biol 2014; 247:1005-18. [DOI: 10.1007/s00232-014-9678-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 05/09/2014] [Indexed: 01/02/2023]
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31
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Agosto MA, Zhang Z, He F, Anastassov IA, Wright SJ, McGehee J, Wensel TG. Oligomeric state of purified transient receptor potential melastatin-1 (TRPM1), a protein essential for dim light vision. J Biol Chem 2014; 289:27019-27033. [PMID: 25112866 PMCID: PMC4175340 DOI: 10.1074/jbc.m114.593780] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 08/03/2014] [Indexed: 11/06/2022] Open
Abstract
Transient receptor potential melastatin-1 (TRPM1) is essential for the light-induced depolarization of retinal ON bipolar cells. TRPM1 likely forms a multimeric channel complex, although almost nothing is known about the structure or subunit composition of channels formed by TRPM1 or any of its close relatives. Recombinant TRPM1 was robustly expressed in insect cells, but only a small fraction was localized to the plasma membrane. Similar intracellular localization was observed when TRPM1 was heterologously expressed in mammalian cells. TRPM1 was affinity-purified from Sf9 cells and complexed with amphipol, followed by detergent removal. In blue native gels and size exclusion chromatography, TRPM1 migrated with a mobility consistent with detergent- or amphipol-bound dimers. Cross-linking experiments were also consistent with a dimeric subunit stoichiometry, and cryoelectron microscopy and single particle analysis without symmetry imposition yielded a model with approximate 2-fold symmetrical features. Finally, electron microscopy of TRPM1-antibody complexes revealed a large particle that can accommodate TRPM1 and two antibody molecules. Taken together, these data indicate that purified TRPM1 is mostly dimeric. The three-dimensional structure of TRPM1 dimers is characterized by a small putative transmembrane domain and a larger domain with a hollow cavity. Blue native gels of solubilized mouse retina indicate that TRPM1 is present in two distinct complexes: one similar in size to the recombinant protein and one much larger. Because dimers are likely not functional ion channels, these results suggest that additional partner subunits participate in forming the transduction channel required for dim light vision and the ON pathway.
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Affiliation(s)
- Melina A Agosto
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Zhixian Zhang
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Feng He
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Ivan A Anastassov
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Sara J Wright
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Jennifer McGehee
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Theodore G Wensel
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030.
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32
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Lentes CJ, Mir SH, Boehm M, Ganea C, Fendler K, Hunte C. Molecular characterization of the Na+/H+-antiporter NhaA from Salmonella Typhimurium. PLoS One 2014; 9:e101575. [PMID: 25010413 PMCID: PMC4092016 DOI: 10.1371/journal.pone.0101575] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/06/2014] [Indexed: 11/29/2022] Open
Abstract
Na+/H+ antiporters are integral membrane proteins that are present in almost every cell and in every kingdom of life. They are essential for the regulation of intracellular pH-value, Na+-concentration and cell volume. These secondary active transporters exchange sodium ions against protons via an alternating access mechanism, which is not understood in full detail. Na+/H+ antiporters show distinct species-specific transport characteristics and regulatory properties that correlate with respective physiological functions. Here we present the characterization of the Na+/H+ antiporter NhaA from Salmonella enterica serovar Thyphimurium LT2, the causing agent of food-born human gastroenteritis and typhoid like infections. The recombinant antiporter was functional in vivo and in vitro. Expression of its gene complemented the Na+-sensitive phenotype of an E. coli strain that lacks the main Na+/H+ antiporters. Purified to homogeneity, the antiporter was a dimer in solution as accurately determined by size-exclusion chromatography combined with multi-angle laser-light scattering and refractive index monitoring. The purified antiporter was fully capable of electrogenic Na+(Li+)/H+-antiport when reconstituted in proteoliposomes and assayed by solid-supported membrane-based electrophysiological measurements. Transport activity was inhibited by 2-aminoperimidine. The recorded negative currents were in agreement with a 1Na+(Li+)/2H+ stoichiometry. Transport activity was low at pH 7 and up-regulation above this pH value was accompanied by a nearly 10-fold decrease of KmNa (16 mM at pH 8.5) supporting a competitive substrate binding mechanism. K+ does not affect Na+ affinity or transport of substrate cations, indicating that selectivity of the antiport arises from the substrate binding step. In contrast to homologous E. coli NhaA, transport activity remains high at pH values above 8.5. The antiporter from S. Typhimurium is a promising candidate for combined structural and functional studies to contribute to the elucidation of the mechanism of pH-dependent Na+/H+ antiporters and to provide insights in the molecular basis of species-specific growth and survival strategies.
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Affiliation(s)
- Christopher J. Lentes
- Institute for Biochemistry and Molecular Biology, ZBMZ, BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Syed H. Mir
- Institute for Biochemistry and Molecular Biology, ZBMZ, BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- Department of Clinical Biochemistry, University of Kashmir, Srinagar, India
| | - Marc Boehm
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Constanta Ganea
- Biophysical Department, Faculty of Medicine, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | - Klaus Fendler
- Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Carola Hunte
- Institute for Biochemistry and Molecular Biology, ZBMZ, BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- * E-mail:
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33
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Ye C, Wang Z, Lu W, Zhong M, Chai Q, Wei Y. Correlation between AcrB trimer association affinity and efflux activity. Biochemistry 2014; 53:3738-46. [PMID: 24854514 PMCID: PMC4067148 DOI: 10.1021/bi5000838] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
![]()
The majority of membrane proteins
function as oligomers. However,
it remains largely unclear how the oligomer stability of protein complexes
correlates with their function. Understanding the relationship between
oligomer stability and activity is essential to protein research and
to virtually all cellular processes that depend on the function of
protein complexes. Proteins make lasting or transient interactions
as they perform their functions. Obligate oligomeric proteins exist
and function exclusively at a specific oligomeric state. Although
oligomerization is clearly critical for such proteins to function,
a direct correlation between oligomer affinity and biological activity
has not yet been reported. Here, we used an obligate trimeric membrane
transporter protein, AcrB, as a model to investigate the correlation
between its relative trimer affinity and efflux activity. AcrB is
a component of the major multidrug efflux system in Escherichia coli. We created six AcrB constructs
with mutations at the transmembrane intersubunit interface, and we
determined their activities using both a drug susceptibility assay
and an ethidium bromide accumulation assay. The relative trimer affinities
of these mutants in detergent micelles were obtained using blue native
polyacrylamide gel electrophoresis. A correlation between the relative
trimer affinity and substrate efflux activity was observed, in which
a threshold trimer stability was required to maintain efflux activity.
The trimer affinity of the wild-type protein was approximately 3 kcal/mol
more stable than the threshold value. Once the threshold was reached,
an additional increase of stability in the range observed had no observable
effect on protein activity.
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Affiliation(s)
- Cui Ye
- Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States
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34
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Vilasi S, Carrotta R, Mangione MR, Campanella C, Librizzi F, Randazzo L, Martorana V, Marino Gammazza A, Ortore MG, Vilasi A, Pocsfalvi G, Burgio G, Corona D, Palumbo Piccionello A, Zummo G, Bulone D, Conway de Macario E, Macario AJL, San Biagio PL, Cappello F. Human Hsp60 with its mitochondrial import signal occurs in solution as heptamers and tetradecamers remarkably stable over a wide range of concentrations. PLoS One 2014; 9:e97657. [PMID: 24830947 PMCID: PMC4022648 DOI: 10.1371/journal.pone.0097657] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 04/21/2014] [Indexed: 11/23/2022] Open
Abstract
It has been established that Hsp60 can accumulate in the cytosol in various pathological conditions, including cancer and chronic inflammatory diseases. Part or all of the cytosolic Hsp60 could be naïve, namely, bear the mitochondrial import signal (MIS), but neither the structure nor the in solution oligomeric organization of this cytosolic molecule has still been elucidated. Here we present a detailed study of the structure and self-organization of naïve cytosolic Hsp60 in solution. Results were obtained by different biophysical methods (light and X ray scattering, single molecule spectroscopy and hydrodynamics) that all together allowed us to assay a wide range of concentrations of Hsp60. We found that Naïve Hsp60 in aqueous solution is assembled in very stable heptamers and tetradecamers at all concentrations assayed, without any trace of monomer presence.
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Affiliation(s)
- Silvia Vilasi
- Institute of Biophysics, National Research Council, Palermo, Italy
| | - Rita Carrotta
- Institute of Biophysics, National Research Council, Palermo, Italy
| | | | - Claudia Campanella
- Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Palermo, Italy
- Euro-Mediterranean Institute of Science and Technology, Palermo, Italy
| | - Fabio Librizzi
- Institute of Biophysics, National Research Council, Palermo, Italy
| | | | | | - Antonella Marino Gammazza
- Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Palermo, Italy
- Euro-Mediterranean Institute of Science and Technology, Palermo, Italy
| | - Maria Grazia Ortore
- Department of Life and Environmental Sciences and National Interuniversity Consortium for the Physical Sciences of Matter, Marche Polytechnic University, Ancona, Italy
| | - Annalisa Vilasi
- Institute of Biosciences and Bioresources, National Research Council, Napoli, Italy
| | - Gabriella Pocsfalvi
- Institute of Biosciences and Bioresources, National Research Council, Napoli, Italy
| | - Giosalba Burgio
- Department of biological chemical and pharmaceutical sciences and technologies, University of Palermo, Palermo, Italy
| | - Davide Corona
- Department of biological chemical and pharmaceutical sciences and technologies, University of Palermo, Palermo, Italy
| | - Antonio Palumbo Piccionello
- Institute of Biophysics, National Research Council, Palermo, Italy
- Department of biological chemical and pharmaceutical sciences and technologies, University of Palermo, Palermo, Italy
| | - Giovanni Zummo
- Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Palermo, Italy
| | - Donatella Bulone
- Institute of Biophysics, National Research Council, Palermo, Italy
| | - Everly Conway de Macario
- Department of Microbiology and Immunology, School of Medicine, University of Maryland at Baltimore, and Institute of Marine and Environmental Technology, Columbus Center, Baltimore, Maryland, United States of America
| | - Alberto J. L. Macario
- Euro-Mediterranean Institute of Science and Technology, Palermo, Italy
- Department of Microbiology and Immunology, School of Medicine, University of Maryland at Baltimore, and Institute of Marine and Environmental Technology, Columbus Center, Baltimore, Maryland, United States of America
| | | | - Francesco Cappello
- Institute of Biophysics, National Research Council, Palermo, Italy
- Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Palermo, Italy
- Euro-Mediterranean Institute of Science and Technology, Palermo, Italy
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35
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Klein RD, Chidawanyika T, Tims HS, Meulia T, Bouchard RA, Pett VB. Chaperone function of two small heat shock proteins from maize. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 221-222:48-58. [PMID: 24656335 DOI: 10.1016/j.plantsci.2014.01.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 01/27/2014] [Accepted: 01/29/2014] [Indexed: 05/22/2023]
Abstract
Small heat shock proteins (sHsps) are molecular chaperones that protect cells from the effect of heat and other stresses. Some sHsps are also expressed at specific stages of development. In plants different classes of sHsps are expressed in the various cellular compartments. While the Class I (cytosolic) sHsps in wheat and pea have been studied extensively, there are fewer experimental data on Class II (cytosolic) sHsps, especially in maize. Here we report the expression and purification of two Class II sHsps from Zea mays ssp. mays L. (cv. Oh43). The two proteins have almost identical sequences, with the significant exception of an additional nine-amino-acid intervening sequence near the beginning of the N-terminus in one of them. Both ZmHsp17.0-CII and ZmHsp17.8-CII oligomerize to form dodecamers at temperatures below heat shock, and we were able to visualize these dodecamers with TEM. There are significant differences between the two sHsps during heat shock at 43°C: ZmHsp17.8-CII dissociates into smaller oligomers than ZmHsp17.0-CII, and ZmHsp17.8-CII is a more efficient chaperone with target protein citrate synthase. Together with the previous observation that ZmHsp17.0-CII but not ZmHsp17.8-CII is expressed during development, we propose different roles in the cell for these two sHsps.
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Affiliation(s)
- Roger D Klein
- Department of Chemistry, The College of Wooster, Wooster, OH 44691, USA.
| | | | - Hannah S Tims
- Department of Chemistry, The College of Wooster, Wooster, OH 44691, USA.
| | - Tea Meulia
- Molecular and Cellular Imaging Center, Ohio Agricultural Research and Development Center, Wooster, OH 44691, USA.
| | - Robert A Bouchard
- Horticulture and Crop Science, Ohio Agricultural Research and Development Center, Wooster, OH 44691, USA.
| | - Virginia B Pett
- Department of Chemistry, The College of Wooster, Wooster, OH 44691, USA.
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Weiland F, Zammit CM, Reith F, Hoffmann P. High resolution two-dimensional electrophoresis of native proteins. Electrophoresis 2014; 35:1893-902. [DOI: 10.1002/elps.201400060] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 02/27/2014] [Accepted: 03/07/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Florian Weiland
- Adelaide Proteomics Centre; University of Adelaide; Adelaide Australia
| | - Carla M. Zammit
- Earth Sciences; University of Queensland; Brisbane Australia
| | - Frank Reith
- School of Earth and Environmental Sciences; University of Adelaide; Adelaide Australia
| | - Peter Hoffmann
- Adelaide Proteomics Centre; University of Adelaide; Adelaide Australia
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Juneja P, Horlacher R, Bertrand D, Krause R, Marger F, Welte W. An internally modulated, thermostable, pH-sensitive Cys loop receptor from the hydrothermal vent worm Alvinella pompejana. J Biol Chem 2014; 289:15130-40. [PMID: 24719323 DOI: 10.1074/jbc.m113.525576] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Cys loop receptors (CLRs) are commonly known as ligand-gated channels that transiently open upon binding of neurotransmitters to modify the membrane potential. However, a class of cation-selective bacterial homologues of CLRs have been found to open upon a sudden pH drop, suggesting further ligands and more functions of the homologues in prokaryotes. Here we report an anion-selective CLR from the hydrothermal vent annelid worm Alvinella pompejana that opens at low pH. A. pompejana expressed sequence tag databases were explored by us, and two full-length CLR sequences were identified, synthesized, cloned, expressed in Xenopus oocytes, and studied by two-electrode voltage clamp. One channel, named Alv-a1-pHCl, yielded functional receptors and opened upon a sudden pH drop but not by other known agonists. Sequence comparison showed that both CLR proteins share conserved characteristics with eukaryotic CLRs, such as an N-terminal helix, a cysteine loop motif, and an intracellular loop intermediate in length between the long loops of other eukaryotic CLRs and those of prokaryotic CLRs. Both full-length Alv-a1-pHCl and a truncated form, termed tAlv-a1-pHCl, lacking 37 amino-terminal residues that precede the N-terminal helix, formed functional channels in oocytes. After pH activation, tAlv-a1-pHCl showed desensitization and was not modulated by ivermectin. In contrast, pH-activated, full-length Alv-a1-pHCl showed a marked rebound current and was modulated significantly by ivermectin. A thermostability assay indicated that purified tAlv-a1-pHCl expressed in Sf9 cells denatured at a higher temperature than the nicotinic acetylcholine receptor from Torpedo californica.
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Affiliation(s)
- Puneet Juneja
- From the Fachbereich Biologie, Universität Konstanz, Universitätsstraβe 10, 78457 Konstanz, Germany
| | | | - Daniel Bertrand
- HiQScreen Sàrl, 6, rte. de Compois, 1222 Vésenaz, Geneva, Switzerland
| | - Ryoko Krause
- HiQScreen Sàrl, 6, rte. de Compois, 1222 Vésenaz, Geneva, Switzerland
| | - Fabrice Marger
- HiQScreen Sàrl, 6, rte. de Compois, 1222 Vésenaz, Geneva, Switzerland
| | - Wolfram Welte
- From the Fachbereich Biologie, Universität Konstanz, Universitätsstraβe 10, 78457 Konstanz, Germany,
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Salzano AM, Novi G, Arioli S, Corona S, Mora D, Scaloni A. Mono-dimensional blue native-PAGE and bi-dimensional blue native/urea-PAGE or/SDS-PAGE combined with nLC–ESI-LIT-MS/MS unveil membrane protein heteromeric and homomeric complexes in Streptococcus thermophilus. J Proteomics 2013; 94:240-61. [DOI: 10.1016/j.jprot.2013.09.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 09/04/2013] [Accepted: 09/14/2013] [Indexed: 02/06/2023]
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Kedrov A, Sustarsic M, de Keyzer J, Caumanns JJ, Wu ZC, Driessen AJ. Elucidating the Native Architecture of the YidC: Ribosome Complex. J Mol Biol 2013; 425:4112-24. [DOI: 10.1016/j.jmb.2013.07.042] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 06/24/2013] [Accepted: 07/09/2013] [Indexed: 10/26/2022]
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40
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Crichton PG, Harding M, Ruprecht JJ, Lee Y, Kunji ERS. Lipid, detergent, and Coomassie Blue G-250 affect the migration of small membrane proteins in blue native gels: mitochondrial carriers migrate as monomers not dimers. J Biol Chem 2013; 288:22163-73. [PMID: 23744064 PMCID: PMC3724668 DOI: 10.1074/jbc.m113.484329] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Blue native gel electrophoresis is a popular method for the determination of the oligomeric state of membrane proteins. Studies using this technique have reported that mitochondrial carriers are dimeric (composed of two ∼32-kDa monomers) and, in some cases, can form physiologically relevant associations with other proteins. Here, we have scrutinized the behavior of the yeast mitochondrial ADP/ATP carrier AAC3 in blue native gels. We find that the apparent mass of AAC3 varies in a detergent- and lipid-dependent manner (from ∼60 to ∼130 kDa) that is not related to changes in the oligomeric state of the protein, but reflects differences in the associated detergent-lipid micelle and Coomassie Blue G-250 used in this technique. Higher oligomeric state species are only observed under less favorable solubilization conditions, consistent with aggregation of the protein. Calibration with an artificial covalent AAC3 dimer indicates that the mass observed for solubilized AAC3 and other mitochondrial carriers corresponds to a monomer. Size exclusion chromatography of purified AAC3 in dodecyl maltoside under blue native gel-like conditions shows that the mass of the monomer is ∼120 kDa, but appears smaller on gels (∼60 kDa) due to the unusually high amount of bound negatively charged dye, which increases the electrophoretic mobility of the protein-detergent-dye micelle complex. Our results show that bound lipid, detergent, and Coomassie stain alter the behavior of mitochondrial carriers on gels, which is likely to be true for other small membrane proteins where the associated lipid-detergent micelle is large when compared with the mass of the protein.
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Affiliation(s)
- Paul G Crichton
- Mitochondrial Biology Unit, Medical Research Council, Hills Road, Cambridge CB2 0XY, United Kingdom
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41
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Duddempudi PK, Nakashe P, Blanton MP, Jansen M. The monomeric state of the proton-coupled folate transporter represents the functional unit in the plasma membrane. FEBS J 2013; 280:2900-15. [PMID: 23601781 DOI: 10.1111/febs.12293] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 03/10/2013] [Accepted: 04/16/2013] [Indexed: 01/20/2023]
Abstract
Folic acid is an essential vitamin required for de novo biosynthesis of nucleotides and amino acids. The proton-coupled folate transporter (PCFT; SLC46A1) has been identified as the major contributor for intestinal folate uptake. It is also involved in folate transport across the blood-brain barrier and into solid tumors. PCFT belongs to the major facilitator superfamily. Major facilitator superfamily members can exist in either monomeric or homo-oligomeric form. Here, we utilized blue native polyacrylamide gel electrophoresis (BN/PAGE) and crosslinking with bi-functional chemicals to investigate the quaternary structure of human PCFT after heterologous expression in Xenopus laevis oocytes and CHO cells. PCFT was expressed in the plasma membrane in both expression systems. The functionality of the utilized PCFT construct was confirmed in oocytes by folic acid induced currents at acidic pH. For both the oocyte and CHO expression system [(3)H]folic acid uptake studies indicated that PCFT was functional. To analyze the oligomeric state of PCFT in the plasma membrane, plasma membranes were isolated by polymerization with colloidal silica and polyacrylic acid and subsequent centrifugation. The digitonin-solubilized non-denatured PCFT migrated during BN/PAGE as a monomer, as judged by comparison with a membrane protein (5-HT(3A) receptor) of known pentameric assembly that was used to create a molecular sizing ladder. The chemical crosslinkers glutaraldehyde and dimethyl adipimidate were not able to covalently link potential higher order PCFT structures to form oligomers that were stable following SDS treatment. Together, our results demonstrate that plasma-membrane PCFT functions as a monomeric protein.
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Affiliation(s)
- Phaneendra K Duddempudi
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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42
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Giudici AM, Molina ML, Ayala JL, Montoya E, Renart ML, Fernández AM, Encinar JA, Ferrer-Montiel AV, Poveda JA, González-Ros JM. Detergent-labile, supramolecular assemblies of KcsA: Relative abundance and interactions involved. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:193-200. [DOI: 10.1016/j.bbamem.2012.09.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 08/22/2012] [Accepted: 09/21/2012] [Indexed: 10/27/2022]
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Tol MB, Deluz C, Hassaine G, Graff A, Stahlberg H, Vogel H. Thermal unfolding of a mammalian pentameric ligand-gated ion channel proceeds at consecutive, distinct steps. J Biol Chem 2012; 288:5756-69. [PMID: 23275379 DOI: 10.1074/jbc.m112.422287] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Pentameric ligand-gated ion channels (LGICs) play an important role in fast synaptic signal transduction. Binding of agonists to the β-sheet-structured extracellular domain opens an ion channel in the transmembrane α-helical region of the LGIC. How the structurally distinct and distant domains are functionally coupled for such central transmembrane signaling processes remains an open question. To obtain detailed information about the stability of and the coupling between these different functional domains, we analyzed the thermal unfolding of a homopentameric LGIC, the 5-hydroxytryptamine receptor (ligand binding, secondary structure, accessibility of Trp and Cys residues, and aggregation), in plasma membranes as well as during detergent extraction, purification, and reconstitution into artificial lipid bilayers. We found a large loss in thermostability correlating with the loss of the lipid bilayer during membrane solubilization and purification. Thermal unfolding of the 5-hydroxytryptamine receptor occurred in consecutive steps at distinct protein locations. A loss of ligand binding was detected first, followed by formation of different transient low oligomeric states of receptor pentamers, followed by partial unfolding of helical parts of the protein, which finally lead to the formation receptor aggregates. Structural destabilization of the receptor in detergents could be partially reversed by reconstituting the receptor into lipid bilayers. Our results are important because they quantify the stability of LGICs during detergent extraction and purification and can be used to create stabilized receptor proteins for structural and functional studies.
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Affiliation(s)
- Menno B Tol
- Laboratory of Physical Chemistry of Polymers and Membranes, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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44
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Abstract
Urea is exploited as a nitrogen source by bacteria, and its breakdown products, ammonia and bicarbonate, are employed to counteract stomach acidity in pathogens such as Helicobacter pylori. Uptake in the latter is mediated by UreI, a UAC (urea amide channel) family member. In the present paper, we describe the structure and function of UACBc, a homologue from Bacillus cereus. The purified channel was found to be permeable not only to urea, but also to other small amides. CD and IR spectroscopy revealed a structure comprising mainly α-helices, oriented approximately perpendicular to the membrane. Consistent with this finding, site-directed fluorescent labelling indicated the presence of seven TM (transmembrane) helices, with a cytoplasmic C-terminus. In detergent, UACBc exists largely as a hexamer, as demonstrated by both cross-linking and size-exclusion chromatography. A 9 Å (1 Å=0.1 nm) resolution projection map obtained by cryo-electron microscopy of two-dimensional crystals shows that the six protomers are arranged in a planar hexameric ring. Each exhibits six density features attributable to TM helices, surrounding a putative central channel, while an additional helix is peripherally located. Bioinformatic analyses allowed individual TM regions to be tentatively assigned to the density features, with the resultant model enabling identification of residues likely to contribute to channel function.
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45
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Silva AJD, Gómez-Mendoza DP, Junqueira M, Domont GB, Ximenes Ferreira Filho E, de Sousa MV, Ricart CAO. Blue native-PAGE analysis of Trichoderma harzianum secretome reveals cellulases and hemicellulases working as multienzymatic complexes. Proteomics 2012; 12:2729-38. [DOI: 10.1002/pmic.201200048] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Adelson Joel da Silva
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
| | - Diana Paola Gómez-Mendoza
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
| | - Magno Junqueira
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
| | | | | | - Marcelo Valle de Sousa
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
| | - Carlos André Ornelas Ricart
- Laboratório de Bioquímica e Química de Proteínas,; Departamento de Biologia Celular; Universidade de Brasília; Brasília DF Brazil
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46
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Ferrandez Y, Monlezun L, Phan G, Benabdelhak H, Benas P, Ulryck N, Falson P, Ducruix A, Picard M, Broutin I. Stoichiometry of the MexA-OprM binding, as investigated by blue native gel electrophoresis. Electrophoresis 2012; 33:1282-7. [PMID: 22589107 DOI: 10.1002/elps.201100541] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Multidrug resistance has become a serious concern in the treatment of bacterial infections. A prominent role is ascribed to the active efflux of xenobiotics out of the bacteria by a tripartite protein machinery. The mechanism of drug extrusion is rather well understood, thanks to the X-ray structures obtained for the Escherichia coli TolC/AcrA/AcrB model system and the related Pseudomonas aeruginosa OprM/MexA/MexB. However, many questions remain unresolved, in particular the stoichiometry of the efflux pump assembly. On the basis of blue native polyacrylamide gel electrophoresis (BN-PAGE) (Wittig et al., Nat. Protoc. 2006, 1, 418-428), we analyzed the binding stoichiometry of both palmitylated and non-palmitylated MexA with the cognate partner OprM trimer at different ratios and detergent conditions. We found that β-octyl glucopyranoside (β-OG) detergent was not suitable for this technique. Then we proved that MexA has to be palmitylated in order to stabilized the complex formation with OprM. Finally, we provided evidence for a two by two (2, 4, 6, or upper) binding of palmitylated MexA per trimer of OprM.
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Affiliation(s)
- Yann Ferrandez
- Laboratoire de Cristallographie et RMN Biologiques, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Paris, France
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47
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Celedon JM, Cline K. Stoichiometry for binding and transport by the twin arginine translocation system. J Cell Biol 2012; 197:523-34. [PMID: 22564412 PMCID: PMC3352945 DOI: 10.1083/jcb.201201096] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 04/12/2012] [Indexed: 11/22/2022] Open
Abstract
Twin arginine translocation (Tat) systems transport large folded proteins across sealed membranes. Tat systems accomplish this feat with three membrane components organized in two complexes. In thylakoid membranes, cpTatC and Hcf106 comprise a large receptor complex containing an estimated eight cpTatC-Hcf106 pairs. Protein transport occurs when Tha4 joins the receptor complex as an oligomer of uncertain size that is thought to form the protein-conducting structure. Here, binding analyses with intact membranes or purified complexes indicate that each receptor complex could bind eight precursor proteins. Kinetic analysis of translocation showed that each precursor-bound site was independently functional for transport, and, with sufficient Tha4, all sites were concurrently active for transport. Tha4 titration determined that ∼26 Tha4 protomers were required for transport of each OE17 (oxygen-evolving complex subunit of 17 kD) precursor protein. Our results suggest that, when fully saturated with precursor proteins and Tha4, the Tat translocase is an ∼2.2-megadalton complex that can individually transport eight precursor proteins or cooperatively transport multimeric precursors.
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Affiliation(s)
- Jose M Celedon
- Horticultural Sciences Department and Plant Molecular and Cellular Biology, University of Florida, Gainesville, FL 32611, USA
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48
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Sergeev M, Godin AG, Kao L, Abuladze N, Wiseman PW, Kurtz I. Determination of membrane protein transporter oligomerization in native tissue using spatial fluorescence intensity fluctuation analysis. PLoS One 2012; 7:e36215. [PMID: 22558387 PMCID: PMC3338697 DOI: 10.1371/journal.pone.0036215] [Citation(s) in RCA: 23] [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: 10/26/2011] [Accepted: 04/02/2012] [Indexed: 11/18/2022] Open
Abstract
Membrane transporter proteins exist in a complex dynamic equilibrium between various oligomeric states that include monomers, dimers, dimer of dimers and higher order oligomers. Given their sub-optical microscopic resolution size, the oligomerization state of membrane transporters is difficult to quantify without requiring tissue disruption and indirect biochemical methods. Here we present the application of a fluorescence measurement technique which combines fluorescence image moment analysis and spatial intensity distribution analysis (SpIDA) to determine the oligomerization state of membrane proteins in situ. As a model system we analyzed the oligomeric state(s) of the electrogenic sodium bicarbonate cotransporter NBCe1-A in cultured cells and in rat kidney. The approaches that we describe offer for the first time the ability to investigate the oligomeric state of membrane transporter proteins in their native state.
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Affiliation(s)
- Mikhail Sergeev
- Department of Physics, McGill University, Montréal, Québec, Canada
| | - Antoine G. Godin
- Department of Physics, McGill University, Montréal, Québec, Canada
| | - Liyo Kao
- David Geffen School Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Natalia Abuladze
- David Geffen School Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Paul W. Wiseman
- Department of Physics, McGill University, Montréal, Québec, Canada
- Department of Chemistry, McGill University, Montréal, Québec, Canada
| | - Ira Kurtz
- David Geffen School Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Brain Research Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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49
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Re-examination of the dimerization state of leucine-rich repeat kinase 2: predominance of the monomeric form. Biochem J 2012; 441:987-94. [PMID: 22047502 DOI: 10.1042/bj20111215] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mutations in the LRRK2 (leucine-rich repeat kinase 2) gene have been identified in PARK8, a major form of autosomal-dominantly inherited familial Parkinson's disease, although the biochemical properties of LRRK2 are not fully understood. It has been proposed that LRRK2 predominantly exists as a homodimer on the basis of the observation that LRRK2, with a theoretical molecular mass of 280 kDa, migrates at 600 kDa (p600 LRRK2) on native polyacrylamide gels. In the present study, we biochemically re-examined the nature of p600 LRRK2 and found that p600 LRRK2 was fractionated with a single peak at ~272 kDa by ultracentrifugation on a glycerol gradient. In addition, p600 LRRK2 behaved similarly to monomeric proteins upon two-dimensional electrophoretic separation. These results suggested a monomeric composition of p600 LRRK2 within cells. The p600 LRRK2 exhibited kinase activity as well as GTP-binding activity, and forced dimerization of LRRK2 neither upregulated its kinase activity nor altered its subcellular localization. Collectively, we conclude that the monomer form of LRRK2 is predominant within cells, and that dimerization is dispensable for its enzymatic activity.
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50
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Türck M, Bierbaum G. Purification and activity testing of the full-length YycFGHI proteins of Staphylococcus aureus. PLoS One 2012; 7:e30403. [PMID: 22276191 PMCID: PMC3262814 DOI: 10.1371/journal.pone.0030403] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 12/20/2011] [Indexed: 11/19/2022] Open
Abstract
Background The YycFG two-component regulatory system (TCS) of Staphylococcus aureus represents the only essential TCS that is almost ubiquitously distributed in Gram-positive bacteria with a low G+C-content. YycG (WalK/VicK) is a sensor histidine-kinase and YycF (WalR/VicR) is the cognate response regulator. Both proteins play an important role in the biosynthesis of the cell envelope and mutations in these proteins have been involved in development of vancomycin and daptomycin resistance. Methodology/Principal Findings Here we present high yield expression and purification of the full-length YycG and YycF proteins as well as of the auxiliary proteins YycH and YycI of Staphylococcus aureus. Activity tests of the YycG kinase and a mutated version, that harbours an Y306N exchange in its cytoplasmic PAS domain, in a detergent-micelle-model and a phosholipid-liposome-model showed kinase activity (autophosphorylation and phosphoryl group transfer to YycF) only in the presence of elevated concentrations of alkali salts. A direct comparison of the activity of the kinases in the liposome-model indicated a higher activity of the mutated YycG kinase. Further experiments indicated that YycG responds to fluidity changes in its microenvironment. Conclusions/Significance The combination of high yield expression, purification and activity testing of membrane and membrane-associated proteins provides an excellent experimental basis for further protein-protein interaction studies and for identification of all signals received by the YycFGHI system.
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Affiliation(s)
- Michael Türck
- Institute of Medical Microbiology, Immunology and Parasitology (IMMIP), University of Bonn, Bonn, Germany
| | - Gabriele Bierbaum
- Institute of Medical Microbiology, Immunology and Parasitology (IMMIP), University of Bonn, Bonn, Germany
- * E-mail:
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