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Bisphenol A Alters the Energy Metabolism of Stromal Cells and Could Promote Bladder Cancer Progression. Cancers (Basel) 2021; 13:cancers13215461. [PMID: 34771623 PMCID: PMC8582525 DOI: 10.3390/cancers13215461] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 10/27/2021] [Accepted: 10/28/2021] [Indexed: 11/23/2022] Open
Abstract
Simple Summary Our research brings new insight on the potential impact of bisphenol A on bladder cancer progression. By evaluating the effects of bisphenol A on the stromal environment of bladder cancer, we aimed to demonstrate that this endocrine disruptor could promote bladder cancer invasion through alteration of the energy metabolism of stromal cells, specifically on bladder fibroblasts and cancer-associated fibroblasts. These findings could modify the understanding of bladder cancer since bladder tissue is not recognized as a hormone-sensitive tissue. Consequently, our study suggests that endocrine disruptors, such as bisphenol A, could impact bladder cancer progression. Abstract Bisphenol A (BPA) is an endocrine-disrupting molecule used in plastics. Through its release in food and the environment, BPA can be found in humans and is mostly excreted in urine. The bladder is therefore continuously exposed to this compound. BPA can bind to multiple cell receptors involved in proliferation, migration and invasion pathways, and exposure to BPA is associated with cancer progression. Considering the physiological concentrations of BPA in urine, we tested the effect of nanomolar concentrations of BPA on the metabolism of bladder fibroblasts and cancer-associated fibroblasts (CAFs). Our results show that BPA led to a decreased metabolism in fibroblasts, which could alter the extracellular matrix. Furthermore, CAF induction triggered a metabolic switch, similar to the Warburg effect described in cancer cells. Additionally, we demonstrated that nanomolar concentrations of BPA could exacerbate this metabolic switch observed in CAFs via an increased glycolytic metabolism, leading to greater acidification of the extracellular environment. These findings suggest that chronic exposure to BPA could promote cancer progression through an alteration of the metabolism of stromal cells.
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Pearson SA, Wachnowsky C, Cowan JA. Defining the mechanism of the mitochondrial Atm1p [2Fe-2S] cluster exporter. Metallomics 2021; 12:902-915. [PMID: 32337520 DOI: 10.1039/c9mt00286c] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Iron-sulfur cluster proteins play key roles in a multitude of physiological processes; including gene expression, nitrogen and oxygen sensing, electron transfer, and DNA repair. Biosynthesis of iron-sulfur clusters occurs in mitochondria on iron-sulfur cluster scaffold proteins in the form of [2Fe-2S] cores that are then transferred to apo targets within metabolic or respiratory pathways. The mechanism by which cytosolic Fe-S cluster proteins mature to their holo forms remains controversial. The mitochondrial inner membrane protein Atm1p can transport glutathione-coordinated iron-sulfur clusters, which may connect the mitochondrial and cytosolic iron-sulfur cluster assembly systems. Herein we describe experiments on the yeast Atm1p/ABCB7 exporter that provide additional support for a glutathione-complexed cluster as the natural physiological substrate and a reflection of the endosymbiotic model of mitochondrial evolution. These studies provide insight on the mechanism of cluster transport and the molecular basis of human disease conditions related to ABCB7. Recruitment of MgATP following cluster binding promotes a structural transition from closed to open conformations that is mediated by coupling helices, with MgATP hydrolysis facilitating the return to the closed state.
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Affiliation(s)
- Stephen A Pearson
- The Ohio State University Biophysics Program, The Ohio State University, 484 West 12th Avenue, Columbus, Ohio, USA43210.
| | - Christine Wachnowsky
- The Ohio State University Biochemistry Program, The Ohio State University, 484 West 12th Avenue, Columbus, Ohio, USA43210
| | - J A Cowan
- The Ohio State University Biophysics Program, The Ohio State University, 484 West 12th Avenue, Columbus, Ohio, USA43210. and The Ohio State University Biochemistry Program, The Ohio State University, 484 West 12th Avenue, Columbus, Ohio, USA43210 and Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, USA43210
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3
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Giddings EL, Champagne DP, Wu MH, Laffin JM, Thornton TM, Valenca-Pereira F, Culp-Hill R, Fortner KA, Romero N, East J, Cao P, Arias-Pulido H, Sidhu KS, Silverstrim B, Kam Y, Kelley S, Pereira M, Bates SE, Bunn JY, Fiering SN, Matthews DE, Robey RW, Stich D, D’Alessandro A, Rincon M. Mitochondrial ATP fuels ABC transporter-mediated drug efflux in cancer chemoresistance. Nat Commun 2021; 12:2804. [PMID: 33990571 PMCID: PMC8121950 DOI: 10.1038/s41467-021-23071-6] [Citation(s) in RCA: 82] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 04/12/2021] [Indexed: 02/04/2023] Open
Abstract
Chemotherapy remains the standard of care for most cancers worldwide, however development of chemoresistance due to the presence of the drug-effluxing ATP binding cassette (ABC) transporters remains a significant problem. The development of safe and effective means to overcome chemoresistance is critical for achieving durable remissions in many cancer patients. We have investigated the energetic demands of ABC transporters in the context of the metabolic adaptations of chemoresistant cancer cells. Here we show that ABC transporters use mitochondrial-derived ATP as a source of energy to efflux drugs out of cancer cells. We further demonstrate that the loss of methylation-controlled J protein (MCJ) (also named DnaJC15), an endogenous negative regulator of mitochondrial respiration, in chemoresistant cancer cells boosts their ability to produce ATP from mitochondria and fuel ABC transporters. We have developed MCJ mimetics that can attenuate mitochondrial respiration and safely overcome chemoresistance in vitro and in vivo. Administration of MCJ mimetics in combination with standard chemotherapeutic drugs could therefore become an alternative strategy for treatment of multiple cancers.
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Affiliation(s)
- Emily L. Giddings
- grid.59062.380000 0004 1936 7689Division of Immunobiology, Department of Medicine, Larner College of Medicine, University of Vermont, Burlington, VT USA
| | - Devin P. Champagne
- grid.59062.380000 0004 1936 7689Division of Immunobiology, Department of Medicine, Larner College of Medicine, University of Vermont, Burlington, VT USA
| | - Meng-Han Wu
- grid.430503.10000 0001 0703 675XDepartment of Immunology and Microbiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO USA
| | - Joshua M. Laffin
- grid.59062.380000 0004 1936 7689Division of Immunobiology, Department of Medicine, Larner College of Medicine, University of Vermont, Burlington, VT USA
| | - Tina M. Thornton
- grid.59062.380000 0004 1936 7689Division of Immunobiology, Department of Medicine, Larner College of Medicine, University of Vermont, Burlington, VT USA
| | - Felipe Valenca-Pereira
- grid.430503.10000 0001 0703 675XDepartment of Immunology and Microbiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO USA
| | - Rachel Culp-Hill
- grid.430503.10000 0001 0703 675XDepartment of Biochemistry and Molecular Genetics, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO USA
| | - Karen A. Fortner
- grid.59062.380000 0004 1936 7689Division of Immunobiology, Department of Medicine, Larner College of Medicine, University of Vermont, Burlington, VT USA
| | - Natalia Romero
- grid.422638.90000 0001 2107 5309Cell Analysis Division, Agilent Technologies, Lexington, MA USA
| | - James East
- grid.59062.380000 0004 1936 7689Division of Immunobiology, Department of Medicine, Larner College of Medicine, University of Vermont, Burlington, VT USA ,grid.59062.380000 0004 1936 7689Department of Radiology, Larner College of Medicine, University of Vermont, Burlington, VT USA
| | - Phoebe Cao
- grid.430503.10000 0001 0703 675XDepartment of Immunology and Microbiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO USA
| | - Hugo Arias-Pulido
- grid.254880.30000 0001 2179 2404Department of Microbiology and Immunology, Geisel School of Medicine, Dartmouth College, Lebanon, NH USA
| | - Karatatiwant S. Sidhu
- grid.59062.380000 0004 1936 7689Department of Chemistry, University of Vermont, Burlington, VT USA
| | - Brian Silverstrim
- grid.59062.380000 0004 1936 7689Division of Immunobiology, Department of Medicine, Larner College of Medicine, University of Vermont, Burlington, VT USA
| | - Yoonseok Kam
- grid.422638.90000 0001 2107 5309Cell Analysis Division, Agilent Technologies, Lexington, MA USA
| | - Shana Kelley
- grid.17063.330000 0001 2157 2938Department of Pharmaceutical Sciences, University of Toronto, Toronto, ON Canada
| | - Mark Pereira
- grid.17063.330000 0001 2157 2938Department of Pharmaceutical Sciences, University of Toronto, Toronto, ON Canada
| | - Susan E. Bates
- grid.239585.00000 0001 2285 2675Division of Hematology/Oncology, Columbia University Medical Center, New York City, NY USA
| | - Janice Y. Bunn
- grid.59062.380000 0004 1936 7689Department of Medical Biostatistics, University of Vermont, Burlington, VT USA
| | - Steven N. Fiering
- grid.254880.30000 0001 2179 2404Department of Microbiology and Immunology, Geisel School of Medicine, Dartmouth College, Lebanon, NH USA
| | - Dwight E. Matthews
- grid.59062.380000 0004 1936 7689Department of Chemistry, University of Vermont, Burlington, VT USA
| | - Robert W. Robey
- grid.48336.3a0000 0004 1936 8075Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD USA
| | - Domink Stich
- grid.430503.10000 0001 0703 675XAdvanced Light Microscopy Core, Neurotechnology Center, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO USA
| | - Angelo D’Alessandro
- grid.430503.10000 0001 0703 675XDepartment of Biochemistry and Molecular Genetics, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO USA
| | - Mercedes Rincon
- grid.59062.380000 0004 1936 7689Division of Immunobiology, Department of Medicine, Larner College of Medicine, University of Vermont, Burlington, VT USA ,grid.430503.10000 0001 0703 675XDepartment of Immunology and Microbiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO USA
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Pearson SA, Cowan JA. Evolution of the human mitochondrial ABCB7 [2Fe-2S](GS) 4 cluster exporter and the molecular mechanism of an E433K disease-causing mutation. Arch Biochem Biophys 2020; 697:108661. [PMID: 33157103 DOI: 10.1016/j.abb.2020.108661] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/08/2020] [Accepted: 10/29/2020] [Indexed: 11/18/2022]
Abstract
Iron-sulfur cluster proteins play key roles in a multitude of cellular processes. Iron-sulfur cofactors are assembled primarily in mitochondria and are then exported to the cytosol by use of an ABCB7 transporter. It has been shown that the yeast mitochondrial transporter Atm1 can export glutathione-coordinated iron-sulfur clusters, [2Fe-2S](SG)4, providing a source of cluster units for cytosolic iron-sulfur cluster assembly systems. This pathway is consistent with the endosymbiotic model of mitochondrial evolution where homologous bacterial heavy metal transporters, utilizing metal glutathione adducts, were adapted for use in eukaryotic mitochondria. Herein, the basis for endosymbiotic evolution of the human cluster export protein (ABCB7) is developed through a BLAST analysis of transporters from ancient proteobacteria. In addition, a functional comparison of native human protein, versus a disease-causing mutant, demonstrates a key role for residue E433 in promoting cluster transport. Dysfunction in mitochondrial export of Fe-S clusters is a likely cause of the disease condition X-linked sideroblastic anemia.
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Affiliation(s)
- Stephen A Pearson
- The Ohio State University Biophysics Program, The Ohio State University, 484 West 12thAvenue, Columbus, OH, 43210, United States
| | - J A Cowan
- The Ohio State University Biophysics Program, The Ohio State University, 484 West 12thAvenue, Columbus, OH, 43210, United States; Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH, 43210, United States. https://chemistry.osu.edu/people/cowan.2
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The scfCDE Operon Encodes a Predicted ABC Importer Required for Fitness and Virulence during Group A Streptococcus Invasive Infection. Infect Immun 2019; 87:IAI.00613-19. [PMID: 31591169 DOI: 10.1128/iai.00613-19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 09/27/2019] [Indexed: 02/08/2023] Open
Abstract
As a strict human pathogen, Streptococcus pyogenes (group A Streptococcus, or GAS) causes a wide range of infections, from superficial to life-threatening diseases, upon dissemination. Thus, it is necessary to gain a better understanding of how GAS successfully overcomes host-mediated challenges and infects various host niches. We previously identified subcutaneous fitness (scf) genes in the clinically relevant wild-type (WT) GAS M1T1 5448 strain that are critical for fitness during murine soft-tissue infection at both 24 h and 48 h postinfection. The uncharacterized locus scfCDE was transcribed as an operon and is predicted to encode an ABC importer for nutrient uptake (e.g., amino acids). Individual scfCDE deletion mutants grew comparably to WT 5448 in rich medium but exhibited reduced fitness during competitive growth in murine soft tissue and in nutrient-limiting chemically defined medium (CDM). A deletion of the permease gene scfD resulted in a monoculture growth defect in CDM that could be rescued by addition of excess peptides, suggesting a role as an amino acid importer. Interestingly, the ΔscfC substrate-binding and ΔscfD permease mutants, but not the ΔscfE ATPase mutant, were highly attenuated in murine soft tissue. Moreover, all three genes were required for GAS survival in human blood, indicating their impact is not limited to superficial infections. As such, scfCDE plays an integral role in enhancing GAS adaptation during localized infection as well as dissemination to deeper host environments. Since scfCDE is conserved throughout Firmicutes, this work may contribute to the development of therapeutic strategies against GAS and other Gram-positive pathogens.
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ABC Transporters Required for Hexose Uptake by Clostridium phytofermentans. J Bacteriol 2019; 201:JB.00241-19. [PMID: 31109990 DOI: 10.1128/jb.00241-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 05/13/2019] [Indexed: 01/02/2023] Open
Abstract
The mechanisms by which bacteria uptake solutes across the cell membrane broadly impact their cellular energetics. Here, we use functional genomic, genetic, and biophysical approaches to reveal how Clostridium (Lachnoclostridium) phytofermentans, a model bacterium that ferments lignocellulosic biomass, uptakes plant hexoses using highly specific, nonredundant ATP-binding cassette (ABC) transporters. We analyze the transcription patterns of its 173 annotated sugar transporter genes to find those upregulated on specific carbon sources. Inactivation of these genes reveals that individual ABC transporters are required for uptake of hexoses and hexo-oligosaccharides and that distinct ABC transporters are used for oligosaccharides versus their constituent monomers. The thermodynamics of sugar binding shows that substrate specificity of these transporters is encoded by the extracellular solute-binding subunit. As sugars are not phosphorylated during ABC transport, we identify intracellular hexokinases based on in vitro activities. These mechanisms used by Clostridia to uptake plant hexoses are key to understanding soil and intestinal microbiomes and to engineer strains for industrial transformation of lignocellulose.IMPORTANCE Plant-fermenting Clostridia are anaerobic bacteria that recycle plant matter in soil and promote human health by fermenting dietary fiber in the intestine. Clostridia degrade plant biomass using extracellular enzymes and then uptake the liberated sugars for fermentation. The main sugars in plant biomass are hexoses, and here, we identify how hexoses are taken in to the cell by the model organism Clostridium phytofermentans We show that this bacterium uptakes hexoses using a set of highly specific, nonredundant ABC transporters. Once in the cell, the hexoses are phosphorylated by intracellular hexokinases. This study provides insight into the functioning of abundant members of soil and intestinal microbiomes and identifies gene targets to engineer strains for industrial lignocellulosic fermentation.
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7
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Methods of reconstitution to investigate membrane protein function. Methods 2018; 147:126-141. [DOI: 10.1016/j.ymeth.2018.02.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 02/13/2018] [Indexed: 02/06/2023] Open
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8
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Wachnowsky C, Cowan JA. In Vitro Studies of Cellular Iron–Sulfur Cluster Biosynthesis, Trafficking, and Transport. Methods Enzymol 2017; 595:55-82. [DOI: 10.1016/bs.mie.2017.06.045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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9
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Wachnowsky C, Fidai I, Cowan JA. Cytosolic iron-sulfur cluster transfer-a proposed kinetic pathway for reconstitution of glutaredoxin 3. FEBS Lett 2016; 590:4531-4540. [PMID: 27859051 DOI: 10.1002/1873-3468.12491] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/03/2016] [Accepted: 11/07/2016] [Indexed: 12/30/2022]
Abstract
Iron-sulfur (Fe-S) clusters are ubiquitously conserved and play essential cellular roles. The mechanism of Fe-S cluster biogenesis involves multiple proteins in a complex pathway. Cluster biosynthesis primarily occurs in the mitochondria, but key Fe-S proteins also exist in the cytosol. One such protein, glutaredoxin 3 (Grx3), is involved in iron regulation, sensing, and mediating [2Fe-2S] cluster delivery to cytosolic protein targets, but the cluster donor for cytosolic Grx3 has not been elucidated. Herein, we delineate the kinetic transfer of [2Fe-2S] clusters into Grx3 from potential cytosolic carrier/scaffold proteins, IscU and Nfu, to evaluate a possible model for Grx3 reconstitution in vivo.
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Affiliation(s)
- Christine Wachnowsky
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA.,The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH, USA
| | - Insiya Fidai
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA.,The Biophysics Graduate Program, The Ohio State University, Columbus, OH, USA
| | - James A Cowan
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA.,The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH, USA.,The Biophysics Graduate Program, The Ohio State University, Columbus, OH, USA
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10
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Hildebrandt E, Khazanov N, Kappes JC, Dai Q, Senderowitz H, Urbatsch IL. Specific stabilization of CFTR by phosphatidylserine. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:289-293. [PMID: 27913277 DOI: 10.1016/j.bbamem.2016.11.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 11/08/2016] [Accepted: 11/28/2016] [Indexed: 10/20/2022]
Abstract
The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR, ABCC7) is a plasma membrane chloride ion channel in the ABC transporter superfamily. CFTR is a key target for cystic fibrosis drug development, and its structural elucidation would advance those efforts. However, the limited in vivo and in vitro stability of the protein, particularly its nucleotide binding domains, has made structural studies challenging. Here we demonstrate that phosphatidylserine uniquely stimulates and thermally stabilizes the ATP hydrolysis function of purified human CFTR. Among several lipids tested, the greatest stabilization was observed with brain phosphatidylserine, which shifted the Tm for ATPase activity from 22.7±0.8°C to 35.0±0.2°C in wild-type CFTR, and from 26.6±0.7°C to 42.1±0.2°C in a more stable mutant CFTR having deleted regulatory insertion and S492P/A534P/I539T mutations. When ATPase activity was measured at 37°C in the presence of brain phosphatidylserine, Vmax for wild-type CFTR was 240±60nmol/min/mg, a rate higher than previously reported and consistent with rates for other purified ABC transporters. The significant thermal stabilization of CFTR by phosphatidylserine may be advantageous in future structural and biophysical studies of CFTR.
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Affiliation(s)
- Ellen Hildebrandt
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA.
| | - Netaly Khazanov
- Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel.
| | - John C Kappes
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA; Birmingham Veterans Medical Center, Research Service, Birmingham, AL 35233, USA.
| | - Qun Dai
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA.
| | - Hanoch Senderowitz
- Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel.
| | - Ina L Urbatsch
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA.
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Bao H, Dalal K, Cytrynbaum E, Duong F. Sequential Action of MalE and Maltose Allows Coupling ATP Hydrolysis to Translocation in the MalFGK2 Transporter. J Biol Chem 2015; 290:25452-60. [PMID: 26338707 DOI: 10.1074/jbc.m115.671826] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Indexed: 01/05/2023] Open
Abstract
ATP-binding cassette (ABC) transporters have evolved an ATP-dependent alternating-access mechanism to transport substrates across membranes. Despite important progress, especially in their structural analysis, it is still unknown how the substrate stimulates ATP hydrolysis, the hallmark of ABC transporters. In this study, we measure the ATP turnover cycle of MalFGK2 in steady and pre-steady state conditions. We show that (i) the basal ATPase activity of MalFGK2 is very low because the cleavage of ATP is rate-limiting, (ii) the binding of open-state MalE to the transporter induces ATP cleavage but leaves release of Pi limiting, and (iii) the additional presence of maltose stimulates release of Pi, and therefore increases the overall ATP turnover cycle. We conclude that open-state MalE stabilizes MalFGK2 in the outward-facing conformation until maltose triggers return to the inward-facing state for substrate and Pi release. This concerted action explains why ATPase activity of MalFGK2 depends on maltose, and why MalE is essential for transport.
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Affiliation(s)
- Huan Bao
- From the Departments of Biochemistry and Molecular Biology and
| | - Kush Dalal
- From the Departments of Biochemistry and Molecular Biology and
| | - Eric Cytrynbaum
- Mathematics, University of British Columbia, Vancouver, British Columbia V6T1Z3, Canada
| | - Franck Duong
- From the Departments of Biochemistry and Molecular Biology and
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13
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Hildebrandt E, Zhang Q, Cant N, Ding H, Dai Q, Peng L, Fu Y, DeLucas LJ, Ford R, Kappes JC, Urbatsch IL. A survey of detergents for the purification of stable, active human cystic fibrosis transmembrane conductance regulator (CFTR). BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2825-37. [PMID: 25065669 DOI: 10.1016/j.bbamem.2014.07.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 07/15/2014] [Accepted: 07/17/2014] [Indexed: 01/12/2023]
Abstract
Structural knowledge of the cystic fibrosis transmembrane conductance regulator (CFTR) requires developing methods to purify and stabilize this aggregation-prone membrane protein above 1mg/ml. Starting with green fluorescent protein- and epitope-tagged human CFTR produced in mammalian cells known to properly fold and process CFTR, we devised a rapid tandem affinity purification scheme to minimize CFTR exposure to detergent in order to preserve its ATPase function. We compared a panel of detergents, including widely used detergents (maltosides, neopentyl glycols (MNG), C12E8, lysolipids, Chaps) and innovative detergents (branched alkylmaltosides, facial amphiphiles) for CFTR purification, function, monodispersity and stability. ATPase activity after reconstitution into proteoliposomes was 2-3 times higher when CFTR was purified using facial amphiphiles. ATPase activity was also demonstrated in purified CFTR samples without detergent removal using a novel lipid supplementation assay. By electron microscopy, negatively stained CFTR samples were monodisperse at low concentration, and size exclusion chromatography showed a predominance of monomer even after CFTR concentration above 1mg/ml. Rates of CFTR aggregation quantified in an electrophoretic mobility shift assay showed that detergents which best preserved reconstituted ATPase activity also supported the greatest stability, with CFTR monomer half-lives of 6-9days in MNG or Chaps, and 12-17days in facial amphiphile. Cryoelectron microscopy of concentrated CFTR in MNG or facial amphiphile confirmed mostly monomeric protein, producing low resolution reconstructions in conformity with similar proteins. These protocols can be used to generate samples of pure, functional, stable CFTR at concentrations amenable to biophysical characterization.
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Affiliation(s)
- Ellen Hildebrandt
- Department of Cell Biology and Biochemistry and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA
| | - Qinghai Zhang
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Natasha Cant
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Haitao Ding
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - Qun Dai
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - Lingling Peng
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Yu Fu
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Lawrence J DeLucas
- Department of Optometry, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - Robert Ford
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - John C Kappes
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA; Department of Microbiology, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA; Department of Pathology, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA; Birmingham Veterans Medical Center, Research Service, Birmingham, AL 35233, USA
| | - Ina L Urbatsch
- Department of Cell Biology and Biochemistry and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA.
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Verchère A, Broutin I, Picard M. Hoechst likes to play hide and seek … use it with caution! Anal Biochem 2013; 440:117-9. [DOI: 10.1016/j.ab.2013.05.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 05/06/2013] [Accepted: 05/14/2013] [Indexed: 11/26/2022]
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15
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Bao H, Duong F. Phosphatidylglycerol directs binding and inhibitory action of EIIAGlc protein on the maltose transporter. J Biol Chem 2013; 288:23666-74. [PMID: 23821551 DOI: 10.1074/jbc.m113.489567] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The signal-transducing protein EIIA(Glc) belongs to the phosphoenolpyruvate carbohydrate phosphotransferase system. In its dephosphorylated state, EIIA(Glc) is a negative regulator for several permeases, including the maltose transporter MalFGK2. How EIIA(Glc) is targeted to the membrane, how it interacts with the transporter, and how it inhibits sugar uptake remain obscure. We show here that acidic phospholipids together with the N-terminal tail of EIIA(Glc) are essential for the high affinity binding of the protein to the transporter. Using protein docking prediction and chemical cross-linking, we demonstrate that EIIA(Glc) binds to the MalK dimer, interacting with both the nucleotide-binding and the C-terminal regulatory domains. Dissection of the ATPase cycle reveals that EIIA(Glc) does not affect the binding of ATP but rather inhibits the capacity of MalK to cleave ATP. We propose a mechanism of maltose transport inhibition by this central amphitropic regulatory protein.
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Affiliation(s)
- Huan Bao
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia V6T1Z3, Canada
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16
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Bao H, Dalal K, Wang V, Rouiller I, Duong F. The maltose ABC transporter: action of membrane lipids on the transporter stability, coupling and ATPase activity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1723-30. [PMID: 23562402 DOI: 10.1016/j.bbamem.2013.03.024] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 03/13/2013] [Accepted: 03/25/2013] [Indexed: 01/25/2023]
Abstract
The coupling between ATP hydrolysis and substrate transport remains a key question in the understanding of ABC-mediated transport. We show using the MalFGK2 complex reconstituted into nanodiscs, that membrane lipids participate directly to the coupling reaction by stabilizing the transporter in a low energy conformation. When surrounded by short acyl chain phospholipids, the transporter is unstable and hydrolyzes large amounts of ATP without inducing maltose. The presence of long acyl chain phospholipids stabilizes the conformational dynamics of the transporter, reduces its ATPase activity and restores dependence on maltose. Membrane lipids therefore play an essential allosteric function, they restrict the transporter ATPase activity to increase coupling to the substrate. In support to the notion, we show that increasing the conformational dynamics of MalFGK2 with mutations in MalF increases the transporter ATPase activity but decreases the maltose transport efficiency.
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Affiliation(s)
- Huan Bao
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, Canada
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17
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Karasawa A, Erkens GB, Berntsson RPA, Otten R, Schuurman-Wolters GK, Mulder FAA, Poolman B. Cystathionine β-synthase (CBS) domains 1 and 2 fulfill different roles in ionic strength sensing of the ATP-binding cassette (ABC) transporter OpuA. J Biol Chem 2011; 286:37280-91. [PMID: 21878634 PMCID: PMC3199475 DOI: 10.1074/jbc.m111.284059] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 08/26/2011] [Indexed: 01/05/2023] Open
Abstract
The cystathionine β-synthase module of OpuA in conjunction with an anionic membrane surface acts as a sensor of internal ionic strength, which allows the protein to respond to osmotic stress. We now show by chemical modification and cross-linking studies that CBS2-CBS2 interface residues are critical for transport activity and/or ionic regulation of transport, whereas CBS1 serves no functional role. We establish that Cys residues in CBS1, CBS2, and the nucleotide-binding domain are more accessible for cross-linking at high than low ionic strength, indicating that these domains undergo conformational changes when transiting between the active and inactive state. Structural analyses suggest that the cystathionine β-synthase module is largely unstructured. Moreover, we could substitute CBS1 by a linker and preserve ionic regulation of transport. These data suggest that CBS1 serves as a linker and the structured CBS2-CBS2 interface forms a hinge point for ionic strength-dependent rearrangements that are transmitted to the nucleotide-binding domain and thereby affect translocation activity.
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Affiliation(s)
- Akira Karasawa
- From the Departments of Biochemistry and Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Guus B. Erkens
- From the Departments of Biochemistry and Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Ronnie P.-A. Berntsson
- From the Departments of Biochemistry and Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Renee Otten
- From the Departments of Biochemistry and Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Gea K. Schuurman-Wolters
- From the Departments of Biochemistry and Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Frans A. A. Mulder
- From the Departments of Biochemistry and Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Bert Poolman
- From the Departments of Biochemistry and Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
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18
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Kawai T, Caaveiro JM, Abe R, Katagiri T, Tsumoto K. Catalytic activity of MsbA reconstituted in nanodisc particles is modulated by remote interactions with the bilayer. FEBS Lett 2011; 585:3533-7. [DOI: 10.1016/j.febslet.2011.10.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Revised: 09/29/2011] [Accepted: 10/07/2011] [Indexed: 11/26/2022]
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19
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Schultz KM, Merten JA, Klug CS. Characterization of the E506Q and H537A dysfunctional mutants in the E. coli ABC transporter MsbA. Biochemistry 2011; 50:3599-608. [PMID: 21462989 PMCID: PMC3128438 DOI: 10.1021/bi101666p] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
MsbA is a member of the ABC transporter superfamily that is specifically found in Gram-negative bacteria and is homologous to proteins involved in both bacterial and human drug resistance. The E506Q and H537A mutations have been introduced and used for crystallization of other members of the ABC transporter protein family, including BmrA and the ATPase domains MalK, HlyB-NBD, and MJ0796, but have not been previously studied in detail or investigated in the MsbA lipid A exporter. We utilized an array of biochemical and EPR spectroscopy approaches to characterize the local and global effects of these nucleotide binding domain mutations on the E. coli MsbA homodimer. The lack of cell viability in an in vivo growth assay confirms that the presence of the E506Q or H537A mutations within MsbA creates a dysfunctional protein. To further investigate the mode of dysfunction, a fluorescent ATP binding assay was used and showed that both mutant proteins maintain their ability to bind ATP, but ATPase assays indicate hydrolysis is severely inhibited by each mutation. EPR spectroscopy data using previously identified and characterized reporter sites within the nucleotide binding domain along with ATP detection assays show that hydrolysis does occur over time in both mutants, though more readily in the H537A protein. DEER spectroscopy demonstrates that both proteins studied are purified in a closed dimer conformation, indicating that events within the cell can induce a stable, closed conformation of the MsbA homodimer that does not reopen even in the absence of nucleotide.
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Affiliation(s)
- Kathryn M. Schultz
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, United States
| | - Jacqueline A. Merten
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, United States
| | - Candice S. Klug
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, United States
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20
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Heme utilization by nontypeable Haemophilus influenzae is essential and dependent on Sap transporter function. J Bacteriol 2011; 193:2527-35. [PMID: 21441512 DOI: 10.1128/jb.01313-10] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial strategies of innate immune evasion and essential metabolic functions are critical for commensal-host homeostasis. Previously, we showed that Sap translocator function is necessary for nontypeable Haemophilus influenzae (NTHI) behaviors that mediate diseases of the human airway. Antimicrobial peptide (AP) lethality is limited by binding mediated by the Sap complex. SapA shares homology with the dipeptide-binding protein (DppA) and the heme-binding lipoprotein (HbpA), both of which have previously been shown to bind the iron-containing compound heme, whose acquisition is essential for Haemophilus survival. Computational modeling revealed conserved SapA residues, similarly modeled to mediate heme binding in HbpA. Here, we directly demonstrate that SapA bound heme and was essential for heme utilization by iron-starved NTHI. Further, the Sap translocator permease mediated heme transport into the bacterial cytoplasm, thus defining a heretofore unknown mechanism of intracytoplasmic membrane heme transport in Haemophilus. Since we demonstrate multiple ligand specificity for the SapA-binding protein, we tested whether APs would compete with heme for SapA binding. We showed that human β-defensins 2 and 3, human cathelicidin LL-37, human neutrophil protein 1, and melittin displaced heme bound to SapA, thus supporting a hierarchy wherein immune evasion supercedes even the needed iron acquisition functions of the Sap system.
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21
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Frelet-Barrand A, Boutigny S, Kunji ERS, Rolland N. Membrane protein expression in Lactococcus lactis. Methods Mol Biol 2010; 601:67-85. [PMID: 20099140 DOI: 10.1007/978-1-60761-344-2_5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Membrane proteins play key roles in cellular physiology, and they are important drug targets. Approximately 25% of all genes identified in sequenced genomes are known to encode membrane proteins; however, the majority have no assigned function. Although the resolution of soluble protein structure has entered the high-throughput stage, only 100 high-resolution structures of membrane proteins have been described until now. Lactococcus lactis is a gram-positive lactic bacterium that has been used traditionally in food fermentations, but it is now used widely in biotechnology for large-scale overproduction of heterologously expressed proteins. Various expression vectors based on either constitutive or inducible promoters exist. The nisin-inducible controlled gene expression (NICE) system is the most suitable for recombinant membrane protein expression allowing for fine control of gene expression based on the autoregulation mechanism of the bacteriocin nisin. Recombinant membrane proteins can be produced with affinity tags for efficient detection and purification from crude membrane protein extracts. The purpose of this chapter is to provide a detailed protocol for the expression of membrane proteins and their detection using the Strep-tag II affinity tag in L. lactis.
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Affiliation(s)
- Annie Frelet-Barrand
- Laboratoire de Physiologie Cellulaire Végétale, CNRS (UMR-5168)/CEA/INRA (UMR-1200), Université Joseph Fourier, iRTSV, CEA-Grenoble, France.
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22
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Kodan A, Shibata H, Matsumoto T, Terakado K, Sakiyama K, Matsuo M, Ueda K, Kato H. Improved expression and purification of human multidrug resistance protein MDR1 from baculovirus-infected insect cells. Protein Expr Purif 2009; 66:7-14. [DOI: 10.1016/j.pep.2009.02.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Revised: 02/10/2009] [Accepted: 02/10/2009] [Indexed: 11/25/2022]
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23
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Abstract
ATP-binding cassette (ABC) transporters constitute a ubiquitous superfamily of integral membrane proteins that are responsible for the ATP-powered translocation of many substrates across membranes. The highly conserved ABC domains of ABC transporters provide the nucleotide-dependent engine that drives transport. By contrast, the transmembrane domains that create the translocation pathway are more variable. Recent structural advances with prokaryotic ABC transporters have provided a qualitative molecular framework for deciphering the transport cycle. An important goal is to develop quantitative models that detail the kinetic and molecular mechanisms by which ABC transporters couple the binding and hydrolysis of ATP to substrate translocation.
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24
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Goetz BA, Perozo E, Locher KP. Distinct gate conformations of the ABC transporter BtuCD revealed by electron spin resonance spectroscopy and chemical cross-linking. FEBS Lett 2008; 583:266-70. [PMID: 19101549 DOI: 10.1016/j.febslet.2008.12.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 12/08/2008] [Accepted: 12/09/2008] [Indexed: 10/21/2022]
Abstract
BtuCD is a type II ABC importer that catalyzes the translocation of vitamin B12 from the periplasm into the cytoplasm of Escherichia coli. Crystal structures of BtuCD and the related HiF (or Hi1470/71) protein from Haemophilus influenzae have revealed distinct conformations of the transmembrane domains that form inner and outer gates. We used electron spin resonance spectroscopy to study the reaction cycle of BtuCD after labeling the protein at residues located at these gates. The results suggest that BtuCD as a prototype type II ABC importer may have a mechanism that is distinct from that of ABC exporters such as Sav1866 or type I ABC importers such as those specific for molybdate (ModBC) or maltose (MalFGK).
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Affiliation(s)
- Birke A Goetz
- Institute of Molecular Biology and Biophysics, ETH Zurich, HPK D14.3, 8093 Zurich, Switzerland
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25
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Doeven MK, van den Bogaart G, Krasnikov V, Poolman B. Probing receptor-translocator interactions in the oligopeptide ABC transporter by fluorescence correlation spectroscopy. Biophys J 2008; 94:3956-65. [PMID: 18212011 PMCID: PMC2367188 DOI: 10.1529/biophysj.107.120964] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2007] [Accepted: 12/21/2007] [Indexed: 11/18/2022] Open
Abstract
The oligopeptide transporter Opp is a five-component ABC uptake system. The extracytoplasmic lipid-anchored substrate-binding protein (or receptor) OppA delivers peptides to an integral membrane complex OppBCDF (or translocator), where, on ATP binding and hydrolysis, translocation across the membrane takes place. OppA and OppBCDF were labeled with fluorescent probes, reconstituted into giant unilamellar vesicles, and the receptor-translocator interactions were investigated by fluorescence correlation spectroscopy. Lateral mobility of OppA was reduced on incorporation of OppBCDF into giant unilamellar vesicles, and decreased even further on the addition of peptide. Fluorescence cross-correlation measurements revealed that OppBCDF distinguished liganded from unliganded OppA, binding only the former. Addition of ATP or its nonhydrolyzable analog AMP-PNP resulted in release of OppA from OppBCDF. In vanadate-trapped "transition state" conditions, OppA also was not bound by OppBCDF. A model is presented in which ATP-binding to OppDF results in donation of peptide to OppBC and simultaneous release of OppA. ATP-hydrolysis would complete the peptide translocation and reset the transporter for another catalytic cycle. Implications in terms of a general transport mechanism for ABC importers and exporters are discussed.
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Affiliation(s)
- Mark K Doeven
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
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26
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Geertsma ER, Nik Mahmood NAB, Schuurman-Wolters GK, Poolman B. Membrane reconstitution of ABC transporters and assays of translocator function. Nat Protoc 2008; 3:256-66. [DOI: 10.1038/nprot.2007.519] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Dawson RJP, Locher KP. Structure of the multidrug ABC transporter Sav1866 from Staphylococcus aureus in complex with AMP-PNP. FEBS Lett 2007; 581:935-8. [PMID: 17303126 DOI: 10.1016/j.febslet.2007.01.073] [Citation(s) in RCA: 345] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 01/26/2007] [Accepted: 01/26/2007] [Indexed: 11/22/2022]
Abstract
Staphylococcus aureus Sav1866 is a bacterial homolog of the human ABC transporter Mdr1 that causes multidrug resistance in cancer cells. We report the crystal structure of Sav1866 in complex with adenosine-5'-(beta,gamma-imido)triphosphate (AMP-PNP) at 3.4A resolution and compare it with the previously determined structure of Sav1866 with bound ADP. Besides differences in the ATP-binding sites, no significant conformational changes were observed. The results confirm that the ATP-bound state of multidrug ABC transporters is coupled to an outward-facing conformation of the transmembrane domains.
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Affiliation(s)
- Roger J P Dawson
- Institute of Molecular Biology and Biophysics, ETH Zurich HPK D14.3, 8093 Zurich, Switzerland
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28
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Abstract
Cells faced with dehydration because of increasing extracellular osmotic pressure accumulate solutes through synthesis or transport. Water follows, restoring cellular hydration and volume. Prokaryotes and eukaryotes possess arrays of osmoregulatory genes and enzymes that are responsible for solute accumulation under osmotic stress. In bacteria, osmosensing transporters can detect increasing extracellular osmotic pressure and respond by mediating the uptake of organic osmolytes compatible with cellular functions ("compatible solutes"). This chapter reviews concepts and methods critical to the identification and study of osmosensing transporters. Like some experimental media, cytoplasm is a "nonideal" solution so the estimation of key solution properties (osmotic pressure, osmolality, water activity, osmolarity, and macromolecular crowding) is essential for studies of osmosensing and osmoregulation. Because bacteria vary widely in osmotolerance, techniques for its characterization provide an essential context for the elucidation of osmosensory and osmoregulatory mechanisms. Powerful genetic, molecular biological, and biochemical tools are now available to aid in the identification and characterization of osmosensory transporters, the genes that encode them, and the osmoprotectants that are their substrates. Our current understanding of osmosensory mechanisms is based on measurements of osmosensory transporter activity performed with intact cells, bacterial membrane vesicles, and proteoliposomes reconstituted with purified transporters. In the quest to elucidate the structural mechanisms of osmosensing and osmoregulation, researchers are now applying the full range of available biophysical, biochemical, and molecular biological tools to osmosensory transporter prototypes.
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Affiliation(s)
- Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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29
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Mahmood NABN, Biemans-Oldehinkel E, Patzlaff JS, Schuurman-Wolters GK, Poolman B. Ion specificity and ionic strength dependence of the osmoregulatory ABC transporter OpuA. J Biol Chem 2006; 281:29830-9. [PMID: 16844687 DOI: 10.1074/jbc.m604907200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ATPase subunit of the osmoregulatory ATP-binding cassette transporter OpuA from Lactococcus lactis has a C-terminal extension, the tandem cystathionine beta-synthase (CBS) domain, which constitutes the sensor that allows the transporter to sense and respond to osmotic stress (Biemans-Oldehinkel, E., Mahmood, N. A. B. N., and Poolman, B. (2006) Proc. Natl. Acad. Sci. U. S. A. 103, 10624-10629). C-terminal of the tandem CBS domain is an 18-residue anionic tail (DIPDEDEVEEIEKEEENK). To investigate the ion specificity of the full transporter, we probed the activity of inside-out reconstituted wild-type OpuA and the anionic tail deletion mutant OpuADelta12; these molecules have the tandem CBS domains facing the external medium. At a mole fraction of 40% of anionic lipids in the membrane, the threshold ionic strength for activation of OpuA was approximately 0.15, irrespective of the electrolyte composition of the medium. At equivalent concentrations, bivalent cations (Mg(2+) and Ba(2+)) were more effective in activating OpuA than NH(4)(+), K(+), Na(+), or Li(+), consistent with an ionic strength-based sensing mechanism. Surprisingly, Rb(+) and Cs(+) were potent inhibitors of wild-type OpuA, and 0.1 mM RbCl was sufficient to completely inhibit the transporter even in the presence of 0.2 M KCl. Rb(+) and Cs(+) were no longer inhibitory in OpuADelta12, indicating that the anionic C-terminal tail participates in the formation of a binding site for large alkali metal ions. Compared with OpuADelta12, wild-type OpuA required substantially less potassium ions (the dominant ion under physiological conditions) for activation. Our data lend new support for the contention that the CBS module in OpuA constitutes the ionic strength sensor whose activity is modulated by the C-terminal anionic tail.
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Affiliation(s)
- N A B Nik Mahmood
- Membrane Enzymology Group, Department of Biochemistry, Groningen Biomolecular Science and Biotechnology Institute and Materials Science Centre, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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30
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Biemans-Oldehinkel E, Mahmood NABN, Poolman B. A sensor for intracellular ionic strength. Proc Natl Acad Sci U S A 2006; 103:10624-9. [PMID: 16815971 PMCID: PMC1502282 DOI: 10.1073/pnas.0603871103] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cystathionine-beta-synthase (CBS) domains are found in >4,000 proteins in species from all kingdoms of life, yet their functions are largely unknown. Tandem CBS domains are associated with membrane transport proteins, most notably members of the ATP-binding cassette (ABC) superfamily; voltage-gated chloride channels and transporters; cation efflux systems; and various enzymes, transcription factors, and proteins of unknown function. We now show that tandem CBS domains in the osmoregulatory ABC transporter OpuA are sensors for ionic strength that control the transport activity through an electrostatic switching mechanism. The on/off state of the transporter is determined by the surface charge of the membrane and the internal ionic strength that is sensed by the CBS domains. By modifying the CBS domains, we can control the ionic strength dependence of the transporter: deleting a stretch of C-terminal anionic residues shifts the ionic strength dependence to higher values, whereas deleting the CBS domains makes the system largely independent of ionic strength. We present a model for the gating of membrane transport by ionic strength and propose a new role for CBS domains.
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Affiliation(s)
- Esther Biemans-Oldehinkel
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Nik A. B. N. Mahmood
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Bert Poolman
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- *To whom correspondence should be addressed. E-mail:
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