1
|
Wang B, Tieleman DP. The structure, self-assembly and dynamics of lipid nanodiscs revealed by computational approaches. Biophys Chem 2024; 309:107231. [PMID: 38569455 DOI: 10.1016/j.bpc.2024.107231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 03/27/2024] [Accepted: 03/28/2024] [Indexed: 04/05/2024]
Abstract
Nanodisc technology is increasingly being used in structural, biochemical and biophysical studies of membrane proteins. The computational approaches have revealed many important features of nanodisc assembly, structures and dynamics. Therefore, we reviewed the application of computational approaches, especially molecular modeling and molecular dyncamics (MD) simulations, to characterize nanodiscs, including the structural models, assembly and disassembly, protocols for modeling, structural properties and dynamics, and protein-lipid interactions in nanodiscs. More amazing computational studies about nanodiscs are looked forward to in the future.
Collapse
Affiliation(s)
- Beibei Wang
- Centre for Advanced Materials Research, Beijing Normal University, Zhuhai 519087, China.
| | - D Peter Tieleman
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Calgary T2N 1N4, Canada.
| |
Collapse
|
2
|
Veit S, Paweletz LC, Günther Pomorski T. Determination of membrane protein orientation upon liposomal reconstitution down to the single vesicle level. Biol Chem 2023; 404:647-661. [PMID: 36857289 DOI: 10.1515/hsz-2022-0325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 02/07/2023] [Indexed: 03/02/2023]
Abstract
Reconstitution of membrane proteins into liposomal membranes represents a key technique in enabling functional analysis under well-defined conditions. In this review, we provide a brief introduction to selected methods that have been developed to determine membrane protein orientation after reconstitution in liposomes, including approaches based on proteolytic digestion with proteases, site-specific labeling, fluorescence quenching and activity assays. In addition, we briefly highlight new strategies based on single vesicle analysis to address the problem of sample heterogeneity.
Collapse
Affiliation(s)
- Sarina Veit
- Department of Molecular Biochemistry , Faculty of Chemistry and Biochemistry , NC 7/174, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum, Germany
| | - Laura Charlotte Paweletz
- Department of Molecular Biochemistry , Faculty of Chemistry and Biochemistry , NC 7/174, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum, Germany
| | - Thomas Günther Pomorski
- Department of Molecular Biochemistry , Faculty of Chemistry and Biochemistry , NC 7/174, Ruhr University Bochum, Universitätsstraße 150, D-44780 Bochum, Germany
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark
| |
Collapse
|
3
|
Zhong Q, Zhang H. Preparation of Small Unilamellar Vesicle Liposomes Using Detergent Dialysis Method. Methods Mol Biol 2023; 2622:49-56. [PMID: 36781748 DOI: 10.1007/978-1-0716-2954-3_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Small unilamellar liposomes are commonly used as model biomembranes and carriers for drug and gene delivery. Although methods which employ mechanical forces or organic solvents can be used to reduce the liposome size and the number of lipid bilayers, they are not suitable options when the purpose is to incorporate biologically active proteins into lipid bilayers or to encapsulate nucleic acid into liposomes. Detergent dialysis is a simple and inexpensive procedure to produce homogeneous small unilamellar vesicles (SUVs). Lipids are solubilized by detergent at a concentration much higher than its critical micellar concentration (CMC) in an aqueous dispersion medium. Free monomer detergent molecules in the dispersion medium are removed during dialysis, while the supramolecular detergent-lipid mixed micelles (MMs) are kept inside the dialysis tubing, leading to dissociation of detergent molecules from MMs. SUVs are formed after the micelle to vesicle transition (MVT).
Collapse
Affiliation(s)
- Qingyue Zhong
- Department of Pharmaceutical Sciences, School of Pharmacy-Boston, MCPHS University, Boston, MA, USA
| | - Hongwei Zhang
- Department of Pharmaceutical Sciences, School of Pharmacy-Boston, MCPHS University, Boston, MA, USA
| |
Collapse
|
4
|
Biophysical quantification of unitary solute and solvent permeabilities to enable translation to membrane science. J Memb Sci 2022. [DOI: 10.1016/j.memsci.2022.121308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
5
|
Hirschi S, Ward TR, Meier WP, Müller DJ, Fotiadis D. Synthetic Biology: Bottom-Up Assembly of Molecular Systems. Chem Rev 2022; 122:16294-16328. [PMID: 36179355 DOI: 10.1021/acs.chemrev.2c00339] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The bottom-up assembly of biological and chemical components opens exciting opportunities to engineer artificial vesicular systems for applications with previously unmet requirements. The modular combination of scaffolds and functional building blocks enables the engineering of complex systems with biomimetic or new-to-nature functionalities. Inspired by the compartmentalized organization of cells and organelles, lipid or polymer vesicles are widely used as model membrane systems to investigate the translocation of solutes and the transduction of signals by membrane proteins. The bottom-up assembly and functionalization of such artificial compartments enables full control over their composition and can thus provide specifically optimized environments for synthetic biological processes. This review aims to inspire future endeavors by providing a diverse toolbox of molecular modules, engineering methodologies, and different approaches to assemble artificial vesicular systems. Important technical and practical aspects are addressed and selected applications are presented, highlighting particular achievements and limitations of the bottom-up approach. Complementing the cutting-edge technological achievements, fundamental aspects are also discussed to cater to the inherently diverse background of the target audience, which results from the interdisciplinary nature of synthetic biology. The engineering of proteins as functional modules and the use of lipids and block copolymers as scaffold modules for the assembly of functionalized vesicular systems are explored in detail. Particular emphasis is placed on ensuring the controlled assembly of these components into increasingly complex vesicular systems. Finally, all descriptions are presented in the greater context of engineering valuable synthetic biological systems for applications in biocatalysis, biosensing, bioremediation, or targeted drug delivery.
Collapse
Affiliation(s)
- Stephan Hirschi
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland.,Molecular Systems Engineering, National Centre of Competence in Research (NCCR), 4002 Basel, Switzerland
| | - Thomas R Ward
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.,Molecular Systems Engineering, National Centre of Competence in Research (NCCR), 4002 Basel, Switzerland
| | - Wolfgang P Meier
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.,Molecular Systems Engineering, National Centre of Competence in Research (NCCR), 4002 Basel, Switzerland
| | - Daniel J Müller
- Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland.,Molecular Systems Engineering, National Centre of Competence in Research (NCCR), 4002 Basel, Switzerland
| | - Dimitrios Fotiadis
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland.,Molecular Systems Engineering, National Centre of Competence in Research (NCCR), 4002 Basel, Switzerland
| |
Collapse
|
6
|
Current problems and future avenues in proteoliposome research. Biochem Soc Trans 2021; 48:1473-1492. [PMID: 32830854 DOI: 10.1042/bst20190966] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/10/2020] [Accepted: 07/14/2020] [Indexed: 12/11/2022]
Abstract
Membrane proteins (MPs) are the gatekeepers between different biological compartments separated by lipid bilayers. Being receptors, channels, transporters, or primary pumps, they fulfill a wide variety of cellular functions and their importance is reflected in the increasing number of drugs that target MPs. Functional studies of MPs within a native cellular context, however, is difficult due to the innate complexity of the densely packed membranes. Over the past decades, detergent-based extraction and purification of MPs and their reconstitution into lipid mimetic systems has been a very powerful tool to simplify the experimental system. In this review, we focus on proteoliposomes that have become an indispensable experimental system for enzymes with a vectorial function, including many of the here described energy transducing MPs. We first address long standing questions on the difficulty of successful reconstitution and controlled orientation of MPs into liposomes. A special emphasis is given on coreconstitution of several MPs into the same bilayer. Second, we discuss recent progress in the development of fluorescent dyes that offer sensitive detection with high temporal resolution. Finally, we briefly cover the use of giant unilamellar vesicles for the investigation of complex enzymatic cascades, a very promising experimental tool considering our increasing knowledge of the interplay of different cellular components.
Collapse
|
7
|
Montigny C, Huang DL, Beswick V, Barbot T, Jaxel C, le Maire M, Zheng JS, Jamin N. Sarcolipin alters SERCA1a interdomain communication by impairing binding of both calcium and ATP. Sci Rep 2021; 11:1641. [PMID: 33452371 PMCID: PMC7810697 DOI: 10.1038/s41598-021-81061-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 12/31/2020] [Indexed: 01/08/2023] Open
Abstract
Sarcolipin (SLN), a single-spanning membrane protein, is a regulator of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA1a). Chemically synthesized SLN, palmitoylated or not (pSLN or SLN), and recombinant wild-type rabbit SERCA1a expressed in S. cerevisiae design experimental conditions that provide a deeper understanding of the functional role of SLN on the regulation of SERCA1a. Our data show that chemically synthesized SLN interacts with recombinant SERCA1a, with calcium-deprived E2 state as well as with calcium-bound E1 state. This interaction hampers the binding of calcium in agreement with published data. Unexpectedly, SLN has also an allosteric effect on SERCA1a transport activity by impairing the binding of ATP. Our results reveal that SLN significantly slows down the E2 to Ca2.E1 transition of SERCA1a while it affects neither phosphorylation nor dephosphorylation. Comparison with chemically synthesized SLN deprived of acylation demonstrates that palmitoylation is not necessary for either inhibition or association with SERCA1a. However, it has a small but statistically significant effect on SERCA1a phosphorylation when various ratios of SLN-SERCA1a or pSLN-SERCA1a are tested.
Collapse
Affiliation(s)
- Cédric Montigny
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, 91198, Gif-sur-Yvette, France.
| | - Dong Liang Huang
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Veronica Beswick
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, 91198, Gif-sur-Yvette, France
- Department of Physics, Evry-Val-d'Essonne University, 91025, Evry, France
| | - Thomas Barbot
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, 91198, Gif-sur-Yvette, France
| | - Christine Jaxel
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, 91198, Gif-sur-Yvette, France
| | - Marc le Maire
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, 91198, Gif-sur-Yvette, France
| | - Ji-Shen Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China.
| | - Nadège Jamin
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, 91198, Gif-sur-Yvette, France
| |
Collapse
|
8
|
Sweet ME, Zhang X, Erdjument-Bromage H, Dubey V, Khandelia H, Neubert TA, Pedersen BP, Stokes DL. Serine phosphorylation regulates the P-type potassium pump KdpFABC. eLife 2020; 9:55480. [PMID: 32955430 PMCID: PMC7535926 DOI: 10.7554/elife.55480] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Accepted: 09/19/2020] [Indexed: 12/22/2022] Open
Abstract
KdpFABC is an ATP-dependent K+ pump that ensures bacterial survival in K+-deficient environments. Whereas transcriptional activation of kdpFABC expression is well studied, a mechanism for down-regulation when K+ levels are restored has not been described. Here, we show that KdpFABC is inhibited when cells return to a K+-rich environment. The mechanism of inhibition involves phosphorylation of Ser162 on KdpB, which can be reversed in vitro by treatment with serine phosphatase. Mutating Ser162 to Alanine produces constitutive activity, whereas the phosphomimetic Ser162Asp mutation inactivates the pump. Analyses of the transport cycle show that serine phosphorylation abolishes the K+-dependence of ATP hydrolysis and blocks the catalytic cycle after formation of the aspartyl phosphate intermediate (E1~P). This regulatory mechanism is unique amongst P-type pumps and this study furthers our understanding of how bacteria control potassium homeostasis to maintain cell volume and osmotic potential.
Collapse
Affiliation(s)
- Marie E Sweet
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| | - Xihui Zhang
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| | - Hediye Erdjument-Bromage
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| | - Vikas Dubey
- PHYLIFE, Physical Life Science, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark
| | - Himanshu Khandelia
- PHYLIFE, Physical Life Science, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark
| | - Thomas A Neubert
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| | - Bjørn P Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - David L Stokes
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| |
Collapse
|
9
|
Peng HM, Valentín-Goyco J, Im SC, Han B, Liu J, Qiao J, Auchus RJ. Expression in Escherichia Coli, Purification, and Functional Reconstitution of Human Steroid 5α-Reductases. Endocrinology 2020; 161:bqaa117. [PMID: 32716491 PMCID: PMC7383974 DOI: 10.1210/endocr/bqaa117] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/03/2020] [Indexed: 11/19/2022]
Abstract
The potent androgen 5α-dihydrotestosterone irreversibly derives from testosterone via the activity of steroid 5α-reductases (5αRs). The major 5αR isoforms in most species, 5αR1 and 5αR2, have not been purified to homogeneity. We report here the heterologous expression of polyhistidine-tagged, codon-optimized human 5αR1 and 5αR2 cDNAs in Escherichia coli. A combination of the nonionic detergents Triton X-100 and Nonidet P-40 enabled solubilization of these extremely hydrophobic integral membrane proteins and facilitated purification with affinity and cation-exchange chromatography methods. For functional reconstitution, we incorporated the purified isoenzymes into Triton X-100-saturated dioleoylphosphatidylcholine liposomes and removed excess detergent with polystyrene beads. Kinetic studies indicated that the 2 isozymes differ in biochemical properties, with 5αR2 having a lower apparent Km for testosterone, androstenedione, progesterone, and 17-hydroxyprogesterone than 5αR1; however, 5αR1 had a greater capacity for steroid conversion, as reflected by a higher Vmax than 5αR2. Both enzymes preferred progesterone as substrate over other steroids, and the catalytic efficiency of purified reconstituted 5αR2 exhibited a sharp pH optimum at pH 5. Intriguingly, we found that the prostate-cancer drug-metabolite 3-keto-∆ 4-abiraterone is metabolized by 5αR1 but not 5αR2, which may serve as a structural basis for isoform selectivity and inhibitor design. The functional characterization results with the purified reconstituted isoenzymes paralleled trends obtained with HEK-293 cell lines stably expressing native 5αR1 and 5αR2. Access to purified human 5αR1 and 5αR2 will advance studies of these important enzymes and might help to clarify their contributions to steroid anabolism and catabolism.
Collapse
Affiliation(s)
- Hwei-Ming Peng
- Division of Metabolism, Endocrinology, & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Juan Valentín-Goyco
- Division of Metabolism, Endocrinology, & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Sang-Choul Im
- Division of Metabolism, Endocrinology, & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
- Veterans Affairs Medical Center, Ann Arbor, MI
| | - Bing Han
- Division of Metabolism, Endocrinology, & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
| | - Jiayan Liu
- Division of Metabolism, Endocrinology, & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Jie Qiao
- Division of Metabolism, Endocrinology, & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
| | - Richard J Auchus
- Division of Metabolism, Endocrinology, & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
- Veterans Affairs Medical Center, Ann Arbor, MI
| |
Collapse
|
10
|
Hakim Elahi S, Abbaszadegan M, Conroy-Ben O. Engineered proteoliposome transporter for treatment of cesium contaminated water. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 704:135317. [PMID: 31812387 DOI: 10.1016/j.scitotenv.2019.135317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 10/28/2019] [Accepted: 10/29/2019] [Indexed: 06/10/2023]
Abstract
Radioactive cesium (137Cs) released from nuclear power plants and nuclear accidents continues to be a worldwide concern, and its removal from water remains a difficult problem. Here, we present the development of an innovative method to remove Cs+ present at low concentrations in water. To achieve this, a proteoliposome transporter was engineered, composed of a membrane-bound potassium uptake protein, Kup from E. coli, which was reconstituted into a liposome vesicle. Cs+ removal (10-100 µg/L) was demonstrated by incubating the constructed proteoliposome in lab-fortified water, followed by ultracentrifugation to remove captured Cs+. Inductively coupled plasma mass spectrometry (ICP-MS) results from testing water spiked with 100 µg/L Cs+ revealed that adding increasing volumes of proteoliposome solution (containing 0.015-1.2 mg of Kup membrane transporter) resulted in 0.29-12.7% removal in a linear fashion. Proteoliposome addition (containing 0.015-0.3 mg of Kup membrane transporter) to water spiked with 10 µg/L Cs+ resulted in 0.65-3.43% removal, while removal by protein-free liposomes was negligible at 0.03%. These results suggest that Kup transporters inserted into the liposomes are mainly responsible for the removal efficiencies. Consequently, a desired removal efficiency can be achieved by adding a higher volume of constructed proteoliposome and subsequently higher mg of Kup transporter to the contaminated water. This provides new insight on the effectiveness and applicability of proteoliposome transporters, and an alternative and a novel contribution to emerging technologies in removing cesium or other metal contaminants undergoing transmembrane transport.
Collapse
Affiliation(s)
- Sepideh Hakim Elahi
- School of Sustainable Engineering and the Built Environment, Ira A. Fulton Schools of Engineering, Arizona State University, United States.
| | - Morteza Abbaszadegan
- School of Sustainable Engineering and the Built Environment, Ira A. Fulton Schools of Engineering, Arizona State University, United States.
| | - Otakuye Conroy-Ben
- School of Sustainable Engineering and the Built Environment, Ira A. Fulton Schools of Engineering, Arizona State University, United States.
| |
Collapse
|
11
|
Porin self-association enables cell-to-cell contact in Providencia stuartii floating communities. Proc Natl Acad Sci U S A 2018; 115:E2220-E2228. [PMID: 29476011 DOI: 10.1073/pnas.1714582115] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The gram-negative pathogen Providencia stuartii forms floating communities within which adjacent cells are in apparent contact, before depositing as canonical surface-attached biofilms. Because porins are the most abundant proteins in the outer membrane of gram-negative bacteria, we hypothesized that they could be involved in cell-to-cell contact and undertook a structure-function relationship study on the two porins of P. stuartii, Omp-Pst1 and Omp-Pst2. Our crystal structures reveal that these porins can self-associate through their extracellular loops, forming dimers of trimers (DOTs) that could enable cell-to-cell contact within floating communities. Support for this hypothesis was obtained by studying the porin-dependent aggregation of liposomes and model cells. The observation that facing channels are open in the two porin structures suggests that DOTs could not only promote cell-to-cell contact but also contribute to intercellular communication.
Collapse
|
12
|
Bian T, Autry JM, Casemore D, Li J, Thomas DD, He G, Xing C. Direct detection of SERCA calcium transport and small-molecule inhibition in giant unilamellar vesicles. Biochem Biophys Res Commun 2016; 481:206-211. [PMID: 27815070 DOI: 10.1016/j.bbrc.2016.10.096] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 10/12/2016] [Indexed: 10/20/2022]
Abstract
We have developed a charge-mediated fusion method to reconstitute the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) in giant unilamellar vesicles (GUV). Intracellular Ca2+ transport by SERCA controls key processes in human cells such as proliferation, signaling, and contraction. Small-molecule effectors of SERCA are urgently needed as therapeutics for Ca2+ dysregulation in human diseases including cancer, diabetes, and heart failure. Here we report the development of a method for efficiently reconstituting SERCA in GUV, and we describe a streamlined protocol based on optimized parameters (e.g., lipid components, SERCA preparation, and activity assay requirements). ATP-dependent Ca2+ transport by SERCA in single GUV was detected directly using confocal fluorescence microscopy with the Ca2+ indicator Fluo-5F. The GUV reconstitution system was validated for functional screening of Ca2+ transport using thapsigargin (TG), a small-molecule inhibitor of SERCA currently in clinical trials as a prostate cancer prodrug. The GUV system overcomes the problem of inhibitory Ca2+ accumulation for SERCA in native and reconstituted small unilamellar vesicles (SUV). We propose that charge-mediated fusion provides a widely-applicable method for GUV reconstitution of clinically-important membrane transport proteins. We conclude that GUV reconstitution is a technological advancement for evaluating small-molecule effectors of SERCA.
Collapse
Affiliation(s)
- Tengfei Bian
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, 2231 6th St SE, Minneapolis, MN 55455, United States; State Key Laboratory of Fine Chemicals, R&D Center of Membrane Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Joseph M Autry
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 321 Church St SE, Minneapolis, MN 55455, United States; Biophysical Technology Center, Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 321 Church St SE, Minneapolis, MN 55455, United States
| | - Denise Casemore
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, 2231 6th St SE, Minneapolis, MN 55455, United States
| | - Ji Li
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 321 Church St SE, Minneapolis, MN 55455, United States; Biophysical Technology Center, Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 321 Church St SE, Minneapolis, MN 55455, United States
| | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 321 Church St SE, Minneapolis, MN 55455, United States
| | - Gaohong He
- State Key Laboratory of Fine Chemicals, R&D Center of Membrane Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Chengguo Xing
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, 2231 6th St SE, Minneapolis, MN 55455, United States.
| |
Collapse
|
13
|
Niroomand H, Venkatesan GA, Sarles SA, Mukherjee D, Khomami B. Lipid-Detergent Phase Transitions During Detergent-Mediated Liposome Solubilization. J Membr Biol 2016; 249:523-38. [DOI: 10.1007/s00232-016-9894-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 03/24/2016] [Indexed: 11/24/2022]
|
14
|
Textor M, Keller S. Calorimetric Quantification of Cyclodextrin-Mediated Detergent Extraction for Membrane-Protein Reconstitution. Methods Enzymol 2016; 567:129-56. [DOI: 10.1016/bs.mie.2015.07.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
|
15
|
Xiong W, Quan C, Zhang X, Wang L, Liu B, Jin L, Fan S. Quantitative analysis of protein orientation in membrane environments by kinase activity. J Biosci Bioeng 2015; 121:242-6. [PMID: 26560241 DOI: 10.1016/j.jbiosc.2015.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 05/25/2015] [Accepted: 06/10/2015] [Indexed: 02/07/2023]
Abstract
AgrC is an integral membrane receptor protein with histidine kinase activity in the accessory gene regulator (agr) quorum-sensing system of Staphylococcus aureus. In this study, proteoliposomes were used as a model to investigate AgrC orientation. Many approaches have been described to determine membrane protein orientation, but they are often complicated and time consuming. In this study, AgrC orientation in liposomes was determined by thiol-reactive reagent labeling and a kinase activity assay. Our results suggest use of a kinase activity assay could get an accurate percentage of functional protein orientation and only cost nearly one-sixth of the time compared with the method based on thiol-reactive reagent labeling. We present an effective and rapid method for determining the orientation of membrane protein kinases like AgrC.
Collapse
Affiliation(s)
- Wen Xiong
- Department of Life Science, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China; Key Laboratory of Biotechnology and Resource Utilization, State Ethnic Affairs Commission and Ministry of Education, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China.
| | - Chunshan Quan
- Department of Life Science, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China; Key Laboratory of Biotechnology and Resource Utilization, State Ethnic Affairs Commission and Ministry of Education, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China.
| | - Xuning Zhang
- School of Biological Engineering, Dalian Polytechnic University, 1 Qinggongyuan, Dalian 116034, China.
| | - Lina Wang
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhong-shan Road, Dalian 116023, China.
| | - Baoquan Liu
- Department of Life Science, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China; Key Laboratory of Biotechnology and Resource Utilization, State Ethnic Affairs Commission and Ministry of Education, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China.
| | - Liming Jin
- Department of Life Science, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China; Key Laboratory of Biotechnology and Resource Utilization, State Ethnic Affairs Commission and Ministry of Education, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China.
| | - Shengdi Fan
- Department of Life Science, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China; Key Laboratory of Biotechnology and Resource Utilization, State Ethnic Affairs Commission and Ministry of Education, Dalian Nationalities University, Economical and Technological Development Zone, Dalian 116600, China.
| |
Collapse
|
16
|
Wang L, Tonggu L. Membrane protein reconstitution for functional and structural studies. SCIENCE CHINA-LIFE SCIENCES 2015; 58:66-74. [PMID: 25576454 DOI: 10.1007/s11427-014-4769-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 10/27/2014] [Indexed: 10/24/2022]
Abstract
Membrane proteins are involved in various critical biological processes, and studying membrane proteins represents a major challenge in protein biochemistry. As shown by both structural and functional studies, the membrane environment plays an essential role for membrane proteins. In vitro studies are reliant on the successful reconstitution of membrane proteins. This review describes the interaction between detergents and lipids that aids the understanding of the reconstitution processes. Then the techniques of detergent removal and a few useful techniques to refine the formed proteoliposomes are reviewed. Finally the applications of reconstitution techniques to study membrane proteins involved in Ca(2+) signaling are summarized.
Collapse
Affiliation(s)
- LiGuo Wang
- Department of Biological Structure, University of Washington, Seattle, Washington, 98195, USA,
| | | |
Collapse
|
17
|
Surma MA, Szczepaniak A, Króliczewski J. Comparative studies on detergent-assisted apocytochrome b6 reconstitution into liposomal bilayers monitored by Zetasizer instruments. PLoS One 2014; 9:e111341. [PMID: 25423011 PMCID: PMC4244035 DOI: 10.1371/journal.pone.0111341] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 10/01/2014] [Indexed: 11/19/2022] Open
Abstract
The present paper is a systematic, comparative study on the reconstitution of an apocytochrome b6 purified from a heterologous system using a detergent-free method and reconstitution into liposomes performed using three different detergents: SDS, Triton X-100 and DM, and two methods of detergent removal by dialysis and using Bio-Beads. The product size, its distribution and zeta potential, and other parameters were monitored throughout the process. We found that zeta potential of proteoliposomes is correlated with reconstitution efficiency and, as such, can serve as a quick and convenient quality control for reconstitution experiments. We also advocate using detergent-free protein purification methods as they allow for an unfettered choice of detergent for reconstitution, which is the most crucial factor influencing the final product parameters.
Collapse
Affiliation(s)
- Michał A. Surma
- Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | | | | |
Collapse
|
18
|
Hughes E, Middleton DA. Comparison of the structure and function of phospholamban and the arginine-14 deficient mutant associated with dilated cardiomyopathy. PLoS One 2014; 9:e106746. [PMID: 25225809 PMCID: PMC4165587 DOI: 10.1371/journal.pone.0106746] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 08/01/2014] [Indexed: 12/20/2022] Open
Abstract
Phospholamban (PLB) is a pentameric protein that plays an important role in regulating cardiac contractility via a reversible inhibitory association with the sarcoplasmic reticulum Ca2+ATPase (SERCA), the enzyme responsible for maintaining correct calcium homeostasis. Here we study the functional and biophysical characteristics of a PLB mutant associated with human dilated cardiomyopathy (DCM), with a deletion of arginine at position 14 (PLBR14Δ). In agreement with recent findings, we find that PLBR14Δ has a reduced inhibitory effect on SERCA compared to wild type PLB (PLBWT) when reconstituted into lipid membranes. The mutation also leads to a large reduction in the protein kinase A-catalysed phosphorylation of Ser-16 in the cytoplasmic domain of PLBR14Δ. Measurements on SERCA co-reconstituted with an equimolar mixture of PLBWT and PLBR14Δ (representing the lethal heterozygous state associated with DCM) indicates that the loss-of-function mutation has a dominant effect on PLBWT functionality and phosphorylation capacity, suggesting that mixed PLBWT/PLBR14Δ pentamers are formed that have characteristics typical of the mutant protein. Structural and biophysical analysis of PLBR14Δ indicates that the mutation perturbs slightly the helical structure of the PLB cytoplasmic domain and reduces its affinity for the phospholipid bilayer surface, thereby altering the orientation of the cytoplasmic domain relative to the wild-type protein. These results indicate that the structure and function consequences of the R14 deletion have profound effects on the regulation of SERCA which may contribute to the aetiology of DCM.
Collapse
Affiliation(s)
- Eleri Hughes
- Department of Chemistry, Lancaster University, Lancaster, United Kingdom
| | - David A Middleton
- Department of Chemistry, Lancaster University, Lancaster, United Kingdom
| |
Collapse
|
19
|
Mulligan C, Fitzgerald GA, Wang DN, Mindell JA. Functional characterization of a Na+-dependent dicarboxylate transporter from Vibrio cholerae. ACTA ACUST UNITED AC 2014; 143:745-59. [PMID: 24821967 PMCID: PMC4035743 DOI: 10.1085/jgp.201311141] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
VcINDY, a bacterial homolog of transporters implicated in lifespan in fruit flies and insulin resistance in mammals, is a high affinity, electrogenic, Na+-dependent dicarboxylate transporter. The SLC13 transporter family, whose members play key physiological roles in the regulation of fatty acid synthesis, adiposity, insulin resistance, and other processes, catalyzes the transport of Krebs cycle intermediates and sulfate across the plasma membrane of mammalian cells. SLC13 transporters are part of the divalent anion:Na+ symporter (DASS) family that includes several well-characterized bacterial members. Despite sharing significant sequence similarity, the functional characteristics of DASS family members differ with regard to their substrate and coupling ion dependence. The publication of a high resolution structure of dimer VcINDY, a bacterial DASS family member, provides crucial structural insight into this transporter family. However, marrying this structural insight to the current functional understanding of this family also demands a comprehensive analysis of the transporter’s functional properties. To this end, we purified VcINDY, reconstituted it into liposomes, and determined its basic functional characteristics. Our data demonstrate that VcINDY is a high affinity, Na+-dependent transporter with a preference for C4- and C5-dicarboxylates. Transport of the model substrate, succinate, is highly pH dependent, consistent with VcINDY strongly preferring the substrate’s dianionic form. VcINDY transport is electrogenic with succinate coupled to the transport of three or more Na+ ions. In contrast to succinate, citrate, bound in the VcINDY crystal structure (in an inward-facing conformation), seems to interact only weakly with the transporter in vitro. These transport properties together provide a functional framework for future experimental and computational examinations of the VcINDY transport mechanism.
Collapse
Affiliation(s)
- Christopher Mulligan
- Membrane Transport Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Gabriel A Fitzgerald
- Membrane Transport Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Da-Neng Wang
- The Helen L. and Martin Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, New York, NY 10016 The Helen L. and Martin Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Joseph A Mindell
- Membrane Transport Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| |
Collapse
|
20
|
Wang L, Quan C, Liu B, Wang J, Xiong W, Zhao P, Fan S. Functional reconstitution of Staphylococcus aureus truncated AgrC histidine kinase in a model membrane system. PLoS One 2013; 8:e80400. [PMID: 24303011 PMCID: PMC3841183 DOI: 10.1371/journal.pone.0080400] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 10/03/2013] [Indexed: 11/18/2022] Open
Abstract
The integral membrane protein AgrC is a histidine kinase whose sensor domains interact with an autoinducing peptide, resulting in a series of downstream responses. In this study, truncated AgrCTM5-6C and AgrCTM5-6C-GFP with GFP as a reporter gene were produced using a bacterial system. Purified AgrCTM5-6C and AgrCTM5-6C-GFP were reconstituted into liposomes by a detergent-mediated method. To achieve high-yield protein incorporation, we investigated the effect of different detergents on protein reconstitution efficiency. The highest incorporation was found with N,N-dimethyldode-cylamine N-oxide during complete liposome solubilization, which resulted in a yield of 85±5%. The COOH-terminus of the protein AgrCTM5-6C was almost exclusively oriented towards the inside of the vesicles. AgrCTM5-6C in proteoliposomes exhibited approximately a 6-fold increase in constitutive activity compared with AgrCTM5-6C in detergent micelles. The reconstitution of AgrCTM5-6C or AgrCTM5-6C-GFP was characterized using dynamic light scattering, fluorescence microscopy, and transmission electron microscopy. Based on the results, the optimal conditions for protein incorporation were defined. These findings contribute to the study of membrane protein structure and function in vitro using a reconstitution system.
Collapse
Affiliation(s)
- Lina Wang
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Chunshan Quan
- Department of Life Science, Dalian Nationalities University, Dalian, China
- The State Ethnic Affairs Commission-Ministry of Education, Dalian, China
- * E-mail:
| | - Baoquan Liu
- Department of Life Science, Dalian Nationalities University, Dalian, China
- The State Ethnic Affairs Commission-Ministry of Education, Dalian, China
| | - Jianfeng Wang
- Department of Life Science, Dalian Nationalities University, Dalian, China
- The State Ethnic Affairs Commission-Ministry of Education, Dalian, China
| | - Wen Xiong
- Department of Life Science, Dalian Nationalities University, Dalian, China
- The State Ethnic Affairs Commission-Ministry of Education, Dalian, China
| | - Pengchao Zhao
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Shengdi Fan
- Department of Life Science, Dalian Nationalities University, Dalian, China
- The State Ethnic Affairs Commission-Ministry of Education, Dalian, China
| |
Collapse
|
21
|
Mulligan C, Mindell JA. Mechanism of transport modulation by an extracellular loop in an archaeal excitatory amino acid transporter (EAAT) homolog. J Biol Chem 2013; 288:35266-76. [PMID: 24155238 DOI: 10.1074/jbc.m113.508408] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Secondary transporters in the excitatory amino acid transporter family terminate glutamatergic synaptic transmission by catalyzing Na(+)-dependent removal of glutamate from the synaptic cleft. Recent structural studies of the aspartate-specific archaeal homolog, Glt(Ph), suggest that transport is achieved by a rigid body, piston-like movement of the transport domain, which houses the substrate-binding site, between the extracellular and cytoplasmic sides of the membrane. This transport domain is connected to an immobile scaffold by three loops, one of which, the 3-4 loop (3L4), undergoes substrate-sensitive conformational change. Proteolytic cleavage of the 3L4 was found to abolish transport activity indicating an essential function for this loop in the transport mechanism. Here, we demonstrate that despite the presence of fully cleaved 3L4, Glt(Ph) is still able to sample conformations relevant for transport. Optimized reconstitution conditions reveal that fully cleaved Glt(Ph) retains some transport activity. Analysis of the kinetics and temperature dependence of transport accompanied by direct measurements of substrate binding reveal that this decreased transport activity is not due to alteration of the substrate binding characteristics but is caused by the significantly reduced turnover rate. By measuring solute counterflow activity and cross-link formation rates, we demonstrate that cleaving 3L4 severely and specifically compromises one or more steps contributing to the movement of the substrate-loaded transport domain between the outward- and inward-facing conformational states, sparing the equivalent step(s) during the movement of the empty transport domain. These results reveal a hitherto unknown role for the 3L4 in modulating an essential step in the transport process.
Collapse
Affiliation(s)
- Christopher Mulligan
- From the Membrane Transport Biophysics Section, Porter Neuroscience Research Center, NINDS, National Institutes of Health, Bethesda, Maryland 20892
| | | |
Collapse
|
22
|
Lee S, Zheng H, Shi L, Jiang QX. Reconstitution of a Kv channel into lipid membranes for structural and functional studies. J Vis Exp 2013:e50436. [PMID: 23892292 DOI: 10.3791/50436] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
To study the lipid-protein interaction in a reductionistic fashion, it is necessary to incorporate the membrane proteins into membranes of well-defined lipid composition. We are studying the lipid-dependent gating effects in a prototype voltage-gated potassium (Kv) channel, and have worked out detailed procedures to reconstitute the channels into different membrane systems. Our reconstitution procedures take consideration of both detergent-induced fusion of vesicles and the fusion of protein/detergent micelles with the lipid/detergent mixed micelles as well as the importance of reaching an equilibrium distribution of lipids among the protein/detergent/lipid and the detergent/lipid mixed micelles. Our data suggested that the insertion of the channels in the lipid vesicles is relatively random in orientations, and the reconstitution efficiency is so high that no detectable protein aggregates were seen in fractionation experiments. We have utilized the reconstituted channels to determine the conformational states of the channels in different lipids, record electrical activities of a small number of channels incorporated in planar lipid bilayers, screen for conformation-specific ligands from a phage-displayed peptide library, and support the growth of 2D crystals of the channels in membranes. The reconstitution procedures described here may be adapted for studying other membrane proteins in lipid bilayers, especially for the investigation of the lipid effects on the eukaryotic voltage-gated ion channels.
Collapse
Affiliation(s)
- Sungsoo Lee
- Department of Cell Biology, University of Texas Southwestern Medical Center at Dallas, USA
| | | | | | | |
Collapse
|
23
|
Protein-protein interactions in calcium transport regulation probed by saturation transfer electron paramagnetic resonance. Biophys J 2013; 103:1370-8. [PMID: 22995510 DOI: 10.1016/j.bpj.2012.08.032] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 08/06/2012] [Accepted: 08/09/2012] [Indexed: 01/05/2023] Open
Abstract
We have used electron paramagnetic resonance (EPR) to probe the homo- and heterooligomeric interactions of reconstituted sarcoplasmic reticulum Ca-ATPase (SERCA) and its regulator phospholamban (PLB). SERCA is responsible for restoring calcium to the sarcoplasmic reticulum to allow muscle relaxation, whereas PLB inhibits cardiac SERCA unless phosphorylated at Ser(16). To determine whether changes in protein association play essential roles in regulation, we detected the microsecond rotational diffusion of both proteins using saturation transfer EPR. Peptide synthesis was used to create a fully functional and monomeric PLB mutant with a spin label rigidly coupled to the backbone of the transmembrane helix, while SERCA was reacted with a Cys-specific spin label. Saturation transfer EPR revealed that sufficiently high lipid/protein ratios minimized self-association for both proteins. Under these dilute conditions, labeled PLB was substantially immobilized after co-reconstitution with unlabeled SERCA, reflecting their association to form the regulatory complex. Ser(16) phosphorylation slightly increased this immobilization. Complementary measurements with labeled SERCA showed no change in mobility after co-reconstitution with unlabeled PLB, regardless of its phosphorylation state. We conclude that phosphorylating monomeric PLB can relieve SERCA inhibition without changes in the oligomeric states of these proteins, indicating a structural rearrangement within the heterodimeric regulatory complex.
Collapse
|
24
|
Paul BK, Guchhait N. Response of an environment-sensitive intramolecular charge transfer probe towards solubilization of liposome membranes by a non-ionic detergent: association and dissociation kinetics. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2012; 96:117-126. [PMID: 22659278 DOI: 10.1016/j.saa.2012.05.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Revised: 04/10/2012] [Accepted: 05/03/2012] [Indexed: 06/01/2023]
Abstract
The present report describes an endeavor to follow the solubilization of DMPC and DMPG liposome membranes by a non-ionic detergent Triton X-100 on the lexicon of environment-sensitive intramolecular charge transfer (ICT) photophysics of an extrinsic molecular probe 5-(4-dimethylamino-phenyl)-penta-2, 4-dienoic acid methyl ester (DPDAME). The prospective applicability of the probe to function as a reporter for detergent-sequestered solubilization of liposome membranes is argued on the basis of comparison of the spectral properties of the probe in various environments. Fluorescence anisotropy study delineates the degree of motional restriction imposed on the probe in different microheterogeneous assemblies. The kinetics of association of the probe with the liposome membranes and the dissociation kinetics of TX-100-sequestered solubilization process of the liposomes have been monitored by the stopped-flow fluorescence technique and the results are rationalized in relevance to fluorescence anisotropy study.
Collapse
Affiliation(s)
- Bijan Kumar Paul
- Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009, India
| | | |
Collapse
|
25
|
Hernandez JM, Stein A, Behrmann E, Riedel D, Cypionka A, Farsi Z, Walla PJ, Raunser S, Jahn R. Membrane fusion intermediates via directional and full assembly of the SNARE complex. Science 2012; 336:1581-4. [PMID: 22653732 PMCID: PMC3677693 DOI: 10.1126/science.1221976] [Citation(s) in RCA: 172] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cellular membrane fusion is thought to proceed through intermediates including docking of apposed lipid bilayers, merging of proximal leaflets to form a hemifusion diaphragm, and fusion pore opening. A membrane-bridging four-helix complex of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediates fusion. However, how assembly of the SNARE complex generates docking and other fusion intermediates is unknown. Using a cell-free reaction, we identified intermediates visually and then arrested the SNARE fusion machinery when fusion was about to begin. Partial and directional assembly of SNAREs tightly docked bilayers, but efficient fusion and an extended form of hemifusion required assembly beyond the core complex to the membrane-connecting linkers. We propose that straining of lipids at the edges of an extended docking zone initiates fusion.
Collapse
Affiliation(s)
- Javier M. Hernandez
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Alexander Stein
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Elmar Behrmann
- Department of Physical Biochemistry, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Dietmar Riedel
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Anna Cypionka
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
- AG Biomolecular Spectroscopy and Single-Molecule Detection, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Zohreh Farsi
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Peter J. Walla
- AG Biomolecular Spectroscopy and Single-Molecule Detection, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
- Department of Biophysical Chemistry, Institute for Physical and Theoretical Chemistry, Technical University of Braunschweig, Hans-Sommer-Str. 10, 38106 Braunschweig, Germany
| | - Stefan Raunser
- Department of Physical Biochemistry, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| |
Collapse
|
26
|
Gustavsson M, Traaseth NJ, Veglia G. Activating and deactivating roles of lipid bilayers on the Ca(2+)-ATPase/phospholamban complex. Biochemistry 2011; 50:10367-74. [PMID: 21992175 DOI: 10.1021/bi200759y] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The physicochemical properties of the lipid bilayer shape the structure and topology of membrane proteins and regulate their biological function. Here, we investigated the functional effects of various lipid bilayer compositions on the sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA) in the presence and absence of its endogenous regulator, phospholamban (PLN). In the cardiac muscle, SERCA hydrolyzes one ATP molecule to translocate two Ca(2+) ions into the SR membrane per enzymatic cycle. Unphosphorylated PLN reduces SERCA's affinity for Ca(2+) and affects the enzymatic turnover. We varied bilayer thickness, headgroup, and fluidity and found that both the maximal velocity (V(max)) of the enzyme and its apparent affinity for Ca(2+) (K(Ca)) are strongly affected. Our results show that (a) SERCA's V(max) has a biphasic dependence on bilayer thickness, reaching maximum activity with 22-carbon lipid chain length, (b) phosphatidylethanolamine (PE) and phosphatidylserine (PS) increase Ca(2+) affinity, and (c) monounsaturated lipids afford higher SERCA V(max) and Ca(2+) affinity than diunsaturated lipids. The presence of PLN removes the activating effect of PE and shifts SERCA's activity profile, with a maximal activity reached in bilayers with 20-carbon lipid chain length. Our results in synthetic lipid systems compare well with those carried out in native SR lipids. Importantly, we found that specific membrane compositions closely reproduce PLN effects (V(max) and K(Ca)) found in living cells, reconciling an ongoing controversy regarding the regulatory role of PLN on SERCA function. Taken with the physiological changes occurring in the SR membrane composition, these studies underscore a possible allosteric role of the lipid bilayers on the SERCA/PLN complex.
Collapse
Affiliation(s)
- Martin Gustavsson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | | | | |
Collapse
|
27
|
Optimized purification of a heterodimeric ABC transporter in a highly stable form amenable to 2-D crystallization. PLoS One 2011; 6:e19677. [PMID: 21602923 PMCID: PMC3094339 DOI: 10.1371/journal.pone.0019677] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 04/06/2011] [Indexed: 12/24/2022] Open
Abstract
Optimized protocols for achieving high-yield expression, purification and reconstitution of membrane proteins are required to study their structure and function. We previously reported high-level expression in Escherichia coli of active BmrC and BmrD proteins from Bacillus subtilis, previously named YheI and YheH. These proteins are half-transporters which belong to the ABC (ATP-Binding Cassette) superfamily and associate in vivo to form a functional transporter able to efflux drugs. In this report, high-yield purification and functional reconstitution were achieved for the heterodimer BmrC/BmrD. In contrast to other detergents more efficient for solubilizing the transporter, dodecyl-ß-D-maltoside (DDM) maintained it in a drug-sensitive and vanadate-sensitive ATPase-competent state after purification by affinity chromatography. High amounts of pure proteins were obtained which were shown either by analytical ultracentrifugation or gel filtration to form a monodisperse heterodimer in solution, which was notably stable for more than one month at 4°C. Functional reconstitution using different lipid compositions induced an 8-fold increase of the ATPase activity (kcat∼5 s−1). We further validated that the quality of the purified BmrC/BmrD heterodimer is suitable for structural analyses, as its reconstitution at high protein densities led to the formation of 2-D crystals. Electron microscopy of negatively stained crystals allowed the calculation of a projection map at 20 Å resolution revealing that BmrC/BmrD might assemble into oligomers in a lipidic environment.
Collapse
|
28
|
Reconstitution in liposome bilayers enhances nucleotide binding affinity and ATP-specificity of TrwB conjugative coupling protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:2160-9. [PMID: 20647001 DOI: 10.1016/j.bbamem.2010.07.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 07/04/2010] [Accepted: 07/07/2010] [Indexed: 11/24/2022]
Abstract
Bacterial conjugative systems code for an essential membrane protein that couples the relaxosome to the DNA transport apparatus, called type IV coupling protein (T4CP). TrwB is the T4CP of the conjugative plasmid R388. In earlier work we found that this protein, purified in the presence of detergents, binds preferentially purine nucleotides trisphosphate. In contrast a soluble truncated mutant TrwBΔN70 binds uniformly all nucleotides tested. In this work, TrwB has been successfully reconstituted into liposomes. The non-membranous portion of the protein is almost exclusively oriented towards the outside of the vesicles. Functional analysis of TrwB proteoliposomes demonstrates that when the protein is inserted into the lipid bilayer the affinity for adenine and guanine nucleotides is enhanced as compared to that of the protein purified in detergent or to the soluble deletion mutant, TrwBΔN70. The protein specificity for adenine nucleotides is also increased. No ATPase activity has been found in TrwB reconstituted in proteoliposomes. This result suggests that the N-terminal transmembrane segment of this T4CP interferes with its ATPase activity and can be taken to imply that the TrwB transmembrane domain plays a regulatory role in its biological activity.
Collapse
|
29
|
Trieber CA, Afara M, Young HS. Effects of phospholamban transmembrane mutants on the calcium affinity, maximal activity, and cooperativity of the sarcoplasmic reticulum calcium pump. Biochemistry 2009; 48:9287-96. [PMID: 19708671 DOI: 10.1021/bi900852m] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Regulation of the SERCA calcium pump by phospholamban (PLB) is largely due to interactions between their respective transmembrane domains. In spite of numerous mutagenesis and kinetic studies, we still do not have a clear mechanistic picture of how PLB influences the calcium transport cycle of SERCA. Herein, we have created alanine mutants for each residue in the transmembrane domain of PLB, we have co-reconstituted these mutants with SERCA into proteoliposomes, and we have performed kinetic simulations of the calcium-dependent ATPase activity isotherms. The PLB transmembrane mutants had a variable effect on the calcium affinity, maximal activity, and cooperativity of SERCA, such that a range of values was observed. Kinetic simulations using a well-established reaction scheme for SERCA then allowed us to correlate the effects on SERCA activity with changes in the reaction scheme rate constants. Only three steps in the reaction scheme were affected by the presence of PLB, namely, binding of the first calcium ion, a subsequent conformational change in SERCA, and binding of the second calcium ion. The ability of wild-type and mutant forms of PLB to alter the apparent calcium affinity of SERCA correlated with a decreased rate of binding of the second calcium ion. In addition, the ability of wild-type and mutant forms of PLB to alter the maximal activity of SERCA correlated with a change in the forward rate constant for the slow conformational change in SERCA following binding of the first calcium ion.
Collapse
Affiliation(s)
- Catharine A Trieber
- Department of Biochemistry and National Institute for Nanotechnology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | | | | |
Collapse
|
30
|
Ouazia D, Bearne SL. A continuous assay for alpha-methylacyl-coenzyme A racemase using circular dichroism. Anal Biochem 2009; 398:45-51. [PMID: 19854148 DOI: 10.1016/j.ab.2009.10.039] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 10/20/2009] [Accepted: 10/21/2009] [Indexed: 12/22/2022]
Abstract
alpha-Methylacyl-coenzyme A racemase (AMACR) catalyzes the epimerization of (2R)- and (2S)-methyl branched fatty acyl-coenzyme A (CoA) thioesters. AMACR is a biomarker for prostate cancer and a putative target for the development of therapeutic agents directed against the disease. To facilitate development of AMACR inhibitors, a continuous circular dichroism (CD)-based assay has been developed. The open reading frame encoding AMACR from Mycobacterium tuberculosis (MCR) was subcloned into a pET15b vector, and the enzyme was overexpressed and purified using metal ion affinity chromatography. The rates of MCR-catalyzed epimerization of either (2R)- or (2S)-ibuprofenoyl-CoA were determined by following the change in ellipticity at 279nm in the presence of octyl-beta-d-glucopyranoside (0.2%). MCR exhibited slightly higher affinity for (2R)-ibuprofenoyl-CoA (K(m)=48+/-5microM, k(cat)=291+/-30s(-1)), but turned over (2S)-ibuprofenoyl-CoA (K(m)=86+/-6microM, k(cat)=450+/-14s(-1)) slightly faster. MCR expressed as a fusion protein bearing an N-terminal His(6)-tag had a catalytic efficiency (k(cat)/K(m)) that was reduced 22% and 47% in the 2S-->2R and 2R-->2S directions, respectively, relative to untagged enzyme. The continuous CD-based assay offers an economical and efficient alternative method to the labor-intensive, fixed-time assays currently used to measure AMACR activity.
Collapse
Affiliation(s)
- Dahmane Ouazia
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5
| | | |
Collapse
|
31
|
Bayburt TH, Sligar SG. Membrane protein assembly into Nanodiscs. FEBS Lett 2009; 584:1721-7. [PMID: 19836392 DOI: 10.1016/j.febslet.2009.10.024] [Citation(s) in RCA: 557] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 10/09/2009] [Indexed: 01/25/2023]
Abstract
Nanodiscs are soluble nanoscale phospholipid bilayers which can self-assemble integral membrane proteins for biophysical, enzymatic or structural investigations. This means for rendering membrane proteins soluble at the single molecule level offers advantages over liposomes or detergent micelles in terms of size, stability, ability to add genetically modifiable features to the Nanodisc structure and ready access to both sides of the phospholipid bilayer domain. Thus the Nanodisc system provides a novel platform for understanding membrane protein function. We provide an overview of the Nanodisc approach and document through several examples many of the applications to the study of the structure and function of integral membrane proteins.
Collapse
Affiliation(s)
- Timothy H Bayburt
- Department of Biochemistry, School of Molecular and Cellular Biology, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA
| | | |
Collapse
|
32
|
Hughes E, Clayton JC, Middleton DA. Cytoplasmic residues of phospholamban interact with membrane surfaces in the presence of SERCA: a new role for phospholipids in the regulation of cardiac calcium cycling? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1788:559-66. [PMID: 19059204 DOI: 10.1016/j.bbamem.2008.10.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 10/10/2008] [Accepted: 10/29/2008] [Indexed: 11/16/2022]
Abstract
The 52-amino acid transmembrane protein phospholamban (PLB) regulates calcium cycling in cardiac cells by forming a complex with the sarco(endo)plasmic reticulum calcium ATPase (SERCA) and reversibly diminishing the rate of calcium uptake by the sarcoplasmic reticulum. The N-terminal cytoplasmic domain of PLB interacts with the cytoplasmic domain of SERCA, but, in the absence of the enzyme, can also associate with the surface of anionic phospholipid membranes. This work investigates whether the cytoplasmic domain of PLB can also associate with membrane surfaces in the presence of SERCA, and whether such interactions could influence the regulation of the enzyme. It is shown using solid-state NMR and isothermal titration calorimetry (ITC) that an N-terminally acetylated peptide representing the first 23 N-terminal amino acids of PLB (PLB1-23) interacts with membranes composed of zwitterionic phosphatidylcholine (PC) and anionic phosphatidylglycerol (PG) lipids in the absence and presence of SERCA. Functional measurements of SERCA in sarcoplasmic reticulum (SR) vesicles, planar SR membranes and reconstituted into PC/PG membranes indicate that PLB1-23 lowers the maximal rate of ATP hydrolysis by acting at the cytoplasmic face of the enzyme. A small, but statistically significant, reduction in the inhibitory effect of the peptide is observed for SERCA reconstituted into PC/PG membranes compared to SERCA in membranes of PC alone. It is suggested that interactions between the cytoplasmic domain of PLB and negatively charged phospholipids might play a role in moderating the regulation of SERCA, with implications for cardiac muscle contractility.
Collapse
Affiliation(s)
- Eleri Hughes
- School of Biological Sciences, University of Liverpool, L69 7ZB Liverpool, UK
| | | | | |
Collapse
|
33
|
Afara MR, Trieber CA, Ceholski DK, Young HS. Peptide inhibitors use two related mechanisms to alter the apparent calcium affinity of the sarcoplasmic reticulum calcium pump. Biochemistry 2008; 47:9522-30. [PMID: 18702513 DOI: 10.1021/bi800880q] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The primary sequence of phospholamban (PLB) has provided a template for the rational design of peptide inhibitors of the sarcoplasmic reticulum calcium ATPase (SERCA). In the transmembrane domain of PLB, there are few polar residues and only one is essential (Asn (34)). Using synthetic peptides, we have previously investigated the role of Asn (34) in the context of simple hydrophobic transmembrane peptides. Herein we propose that the role of Asn in SERCA inhibition is position-sensitive and dependent upon the distribution of hydrophobic residues. To test this hypothesis, we synthesized a series of transmembrane peptides based on a 24 amino acid polyalanine sequence having either an alternating Leu-Ala sequence (Leu 12) or Leu residues at the native positions found in PLB (Leu 9). Asn-containing Leu 9 and Leu 12 peptides were synthesized with a single Asn residue located either one amino acid (N+/-1) or one turn of the helix (N+/-4) in either direction from its native position. Co-reconstitution of these peptides with SERCA into proteoliposomes revealed effects on the apparent calcium affinity and cooperativity of SERCA that correlated with the positions of the Asn and Leu residues. The most inhibitory peptides increased the cooperativity of SERCA as indicated by the Hill coefficients, suggesting that calcium-dependent reversibility is an inherent part of the inhibitory mechanism. Kinetic simulations combined with molecular modeling of the interaction between the peptides and SERCA reveal two related mechanisms of inhibition. Peptides that resemble PLB use the same inhibitory mechanism, whereas peptides that are more divergent from PLB alter an additional step in the calcium transport cycle.
Collapse
Affiliation(s)
- Michael R Afara
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
| | | | | | | |
Collapse
|
34
|
Bernat V, Ringard-Lefebvre C, Bas GL, Perly B, Djedaïni-Pilard F, Lesieur S. Inclusion complex of n-octyl beta-D-glucopyranoside and alpha-cyclodextrin in aqueous solutions: thermodynamic and structural characterization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:3140-3149. [PMID: 18324857 DOI: 10.1021/la7034906] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Complex formation between octyl beta-D-glucopyranoside (OG) and alpha-cyclodextrin (alphaCD) was investigated on the basis of three highly accurate and appropriate experimental techniques. First, surface tension measurements showed that alphaCD directly acts on the surfactant monomers in the aqueous phase, leading to progressive depletion of the air-water interface with increasing cyclodextrin contents. Significant shift of OG critical micelle concentration (cmc) was consequently observed: the higher alphaCD concentration, the higher the cmc value. Experiments performed at surfactant and cyclodextrin concentrations in the Gibbs regime of surface tension versus OG content were performed on one hand to establish Job's plot that showed 1:1 stoichiometry of the OG-alphaCD complex and on the other hand to calculate the association constant found equal to (1.85 +/- 0.35) x 10(3) L mol(-1). An inclusion process of the surfactant alkyl residue within the cyclodextrin cavity was confirmed by one-dimensional (1)H NMR, and the structure of the mixed assembly was extensively characterized by two-dimensional NOESY (1)H NMR. OG penetrates alphaCD so that its hydrocarbon chain is embedded inside the cyclodextrin cavity, and its polar head as well as the alpha-methylene group emerges outside the alphaCD secondary face. Solubility behavior of the OG-alphaCD complex in a wide range of host-guest ratios and concentrations was finally examined by turbidity recording and optical microscopy. At very low free cyclodextrin levels in the solution, the complex presented high solubility behavior up to more than 70 mM. By increasing nonassociated alphaCD in the mixture, propensity of the cyclodextrin molecules to crystallize was observed at concentrations far below the 100 mM aqueous solubility of the pure cyclodextrin. The hexagonal shape of the crystals seen in the optical microscopy images suggested they were, partially at least, composed of the solid complex.
Collapse
Affiliation(s)
- Valérie Bernat
- Laboratoire Physico-Chimie Pharmacotechnie Biopharmacie, Faculté de pharmacie, UMR CNRS 8612, Université Paris-Sud, 5 rue Jean-Baptiste Clément, F-92296 Châtenay-Malabry Cedex, France
| | | | | | | | | | | |
Collapse
|
35
|
Powl AM, East JM, Lee AG. Anionic phospholipids affect the rate and extent of flux through the mechanosensitive channel of large conductance MscL. Biochemistry 2008; 47:4317-28. [PMID: 18341289 DOI: 10.1021/bi702409t] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanosensitive channel of large conductance MscL from Escherichia coli has been reconstituted into sealed vesicles, and the effects of lipid structure on the flux of the fluorescent molecule calcein through the open channel have been studied. The channel was opened by reaction of the G22C mutant of MscL with the reagent [2-(triethylammonium)ethyl]methanethiosulfonate (MTSET) which introduces five positive charges within the pore constriction. Flux through the channel was small when the lipid was phosphatidylcholine, but addition of the anionic lipids phosphatidylglycerol, phosphatidic acid, or cardiolipin up to 50 mol % resulted in increases in the amplitudes and rates of release of calcein. Similar effects were seen when either wild-type MscL or the G22C mutant was opened by osmotic pressure difference; rates of release of calcein were very slow in the absence of anionic lipid but increased with increasing concentrations of phosphatidylglycerol to 50 mol %. The observed partial release of trapped calcein following activation of MscL was attributed to the formation of a long-lived subconductance state of MscL following channel opening. Effects of anionic lipid were attributed to an increase in the rate of the transition from closed to fully open state and to a decrease in the rate of the transition from the fully open state to the subconductance state. Higher concentrations of anionic lipid led to a decrease in the rate and amplitude of release of calcein, possibly due to a decreased rate of flux through the open channel. In mixtures with anionic lipids, phosphatidylethanolamine resulted in lower rates and amplitude of release than phosphatidylcholine.
Collapse
Affiliation(s)
- Andrew M Powl
- School of Biological Sciences, University of Southampton, Southampton, SO16 7PX, UK
| | | | | |
Collapse
|
36
|
Tadini-Buoninsegni F, Bartolommei G, Moncelli MR, Fendler K. Charge transfer in P-type ATPases investigated on planar membranes. Arch Biochem Biophys 2008; 476:75-86. [PMID: 18328799 DOI: 10.1016/j.abb.2008.02.031] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 02/19/2008] [Accepted: 02/20/2008] [Indexed: 11/18/2022]
Abstract
Planar lipid bilayers, e.g., black lipid membranes (BLM) and solid supported membranes (SSM), have been employed to investigate charge movements during the reaction cycle of P-type ATPases. The BLM/SSM method allows a direct measurement of the electrical currents generated by the cation transporter following chemical activation by a substrate concentration jump. The electrical current transients provides information about the reaction mechanism of the enzyme. In particular, the BLM/SSM technique allows identification of electrogenic steps which in turn may be used to localize ion translocation during the reaction cycle of the pump. In addition, using the high time resolution of the technique, especially when rapid activation via caged ATP is employed, rate constants of electrogenic and electroneutral steps can be determined. In the present review, we will discuss the main results obtained by the BLM and SSM methods and how they have contributed to unravel the transport mechanism of P-type ATPases.
Collapse
|
37
|
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]
|
38
|
Fernandes F, Neves P, Gameiro P, Loura LMS, Prieto M. Ciprofloxacin interactions with bacterial protein OmpF: modelling of FRET from a multi-tryptophan protein trimer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2822-30. [PMID: 17900524 DOI: 10.1016/j.bbamem.2007.07.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2007] [Revised: 06/25/2007] [Accepted: 07/25/2007] [Indexed: 11/17/2022]
Abstract
The outer membrane protein F (OmpF) is known to play an important role in the uptake of fluoroquinolone antibiotics by bacteria. In this study, the degree of binding of the fluoroquinolone antibiotic ciprofloxacin to OmpF in a lipid membrane environment is quantified using a methodology based on Förster resonance energy transfer (FRET). Analysis of the fluorescence quenching of OmpF is complex as each OmpF monomer presents two tryptophans at different positions, thus sensing two different distributions of acceptors in the bilayer plane. Specific FRET formalisms were derived accounting for the different energy transfer contributions to quenching of each type of tryptophan of OmpF, allowing the recovery of upper and lower boundaries for the ciprofloxacin-OmpF binding constant (K(B)). log (K(B)) was found to lie in the range 3.15-3.62 or 3.58-4.00 depending on the location for the ciprofloxacin binding site assumed in the FRET modelling, closer to the centre or to the periphery of the OmpF trimer, respectively. This methodology is suitable for the analysis of FRET data obtained with similar protein systems and can be readily adapted to different geometries.
Collapse
Affiliation(s)
- Fábio Fernandes
- Centro de Química-Física Molecular, Instituto Superior Técnico, Lisbon, Portugal
| | | | | | | | | |
Collapse
|
39
|
Hughes E, Clayton JC, Kitmitto A, Esmann M, Middleton DA. Solid-state NMR and functional measurements indicate that the conserved tyrosine residues of sarcolipin are involved directly in the inhibition of SERCA1. J Biol Chem 2007; 282:26603-13. [PMID: 17616528 DOI: 10.1074/jbc.m611668200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transmembrane protein sarcolipin regulates calcium storage in the sarcoplasmic reticulum of skeletal and cardiac muscle cells by modulating the activity of sarco(endo)plasmic reticulum Ca(2+)-ATPases (SERCAs). The highly conserved C-terminal region ((27)RSYQY-COOH) of sarcolipin helps to target the protein to the sarcoplasmic reticulum membrane and may also participate in the regulatory interaction between sarcolipin and SERCA. Here we used solid-state NMR measurements of local protein dynamics to illuminate the direct interaction between the Tyr(29) and Tyr(31) side groups of sarcolipin and skeletal muscle Ca(2+)-ATPase (SERCA1a) embedded in dioleoylphosphatidylcholine bilayers. Further solid-state NMR experiments together with functional measurements on SERCA1a in the presence of NAc-RSYQY, a peptide representing the conserved region of sarcolipin, suggest that the peptide binds to the same site as the parent protein at the luminal face of SERCA1a, where it reduces V(max) for calcium transport and inhibits ATP hydrolysis with an IC(50) of approximately 200 microM. The inhibitory effect of NAc-RSYQY is remarkably sequence-specific, with the native aromatic residues being essential for optimal inhibitory activity. This combination of physical and functional measurements highlights the importance of aromatic and polar residues in the C-terminal region of sarcolipin for regulating calcium cycling and muscle contractility.
Collapse
Affiliation(s)
- Eleri Hughes
- School of Biological Sciences, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom
| | | | | | | | | |
Collapse
|
40
|
Hung Y, Layton M, Voskoboinik I, Mercer J, Camakaris J. Purification and membrane reconstitution of catalytically active Menkes copper-transporting P-type ATPase (MNK; ATP7A). Biochem J 2007; 401:569-79. [PMID: 17009961 PMCID: PMC1820817 DOI: 10.1042/bj20060924] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The MNK (Menkes disease protein; ATP7A) is a major copper- transporting P-type ATPase involved in the delivery of copper to cuproenzymes in the secretory pathway and the efflux of excess copper from extrahepatic tissues. Mutations in the MNK (ATP7A) gene result in Menkes disease, a fatal neurodegenerative copper deficiency disorder. Currently, detailed biochemical and biophysical analyses of MNK to better understand its mechanisms of copper transport are not possible due to the lack of purified MNK in an active form. To address this issue, we expressed human MNK with an N-terminal Glu-Glu tag in Sf9 [Spodoptera frugiperda (fall armyworm) 9] insect cells and purified it by antibody affinity chromatography followed by size-exclusion chromatography in the presence of the non-ionic detergent DDM (n-dodecyl beta-D-maltopyranoside). Formation of the classical vanadate-sensitive phosphoenzyme by purified MNK was activated by Cu(I) [EC50=0.7 microM; h (Hill coefficient) was 4.6]. Furthermore, we report the first measurement of Cu(I)-dependent ATPase activity of MNK (K0.5=0.6 microM; h=5.0). The purified MNK demonstrated active ATP-dependent vectorial 64Cu transport when reconstituted into soya-bean asolectin liposomes. Together, these data demonstrated that Cu(I) interacts with MNK in a co-operative manner and with high affinity in the sub-micromolar range. The present study provides the first biochemical characterization of a purified full-length mammalian copper-transporting P-type ATPase associated with a human disease.
Collapse
Affiliation(s)
- Ya Hui Hung
- *Department of Genetics, University of Melbourne, VIC 3010, Australia
| | - Meredith J. Layton
- †Joint Proteomics Laboratory, Ludwig Institute for Cancer Research and Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3050, Australia
| | - Ilia Voskoboinik
- *Department of Genetics, University of Melbourne, VIC 3010, Australia
| | - Julian F. B. Mercer
- ‡Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, Deakin University, Burwood, VIC 3125, Australia
| | - James Camakaris
- *Department of Genetics, University of Melbourne, VIC 3010, Australia
- To whom correspondence should be addressed (email )
| |
Collapse
|
41
|
Tadini-Buoninsegni F, Bartolommei G, Moncelli MR, Guidelli R, Inesi G. Pre-steady state electrogenic events of Ca2+/H+ exchange and transport by the Ca2+-ATPase. J Biol Chem 2006; 281:37720-7. [PMID: 17032645 DOI: 10.1074/jbc.m606040200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Native or recombinant SERCA (sarco(endo)plasmic reticulum Ca(2+) ATPase) was adsorbed on a solid supported membrane and then activated with Ca(2+) and ATP concentration jumps through rapid solution exchange. The resulting electrogenic events were recorded as electrical currents flowing along the external circuit. Current transients were observed following Ca(2+) jumps in the absence of ATP and following ATP jumps in the presence of Ca(2+). The related charge movements are attributed to Ca(2+) reaching its binding sites in the ground state of the enzyme (E(1)) and to its vectorial release from the enzyme phosphorylated by ATP (E(2)P). The Ca(2+) concentration and pH dependence as well as the time frames of the observed current transients are consistent with equilibrium and pre-steady state biochemical measurements of sequential steps within a single enzymatic cycle. Numerical integration of the current transients recorded at various pH values reveal partial charge compensation by H(+) in exchange for Ca(2+) at acidic (but not at alkaline) pH. Most interestingly, charge movements induced by Ca(2+) and ATP vary over different pH ranges, as the protonation probability of residues involved in Ca(2+)/H(+) exchange is lower in the E(1) than in the E(2)P state. Our single cycle measurements demonstrate that this difference contributes directly to the reduction of Ca(2+) affinity produced by ATP utilization and results in the countertransport of two Ca(2+) and two H(+) within each ATPase cycle at pH 7.0. The effects of site-directed mutations indicate that Glu-771 and Asp-800, within the Ca(2+) binding domain, are involved in the observed Ca(2+)/H(+) exchange.
Collapse
|
42
|
Li C, Duan W, Yang F, Zhang X. Caveolin-3-anchored microdomains at the rabbit sarcoplasmic reticulum membranes. Biochem Biophys Res Commun 2006; 344:1135-40. [PMID: 16647041 DOI: 10.1016/j.bbrc.2006.04.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Accepted: 04/05/2006] [Indexed: 11/28/2022]
Abstract
It is generally believed that sphingomyelin- and cholesterol-enriched microdomains can be isolated as detergent-resistant membranes (DRMs) from plasma membrane and organelle membranes. Here, we describe the isolation and characterization of microdomains from sarcoplasmic reticulum (SR) membranes. These SR-derived detergent-resistant membranes (SR-DRMs) enriched in sphingomyelin and cholesterol have a low buoyant density. Immunofluorescence microscopy of SR membranes shows the presence of caveolin-3 in the SR, known as a marker protein of caveolae at plasma membrane. We also demonstrated that significant amount of SERCAs together with caveolin-3 associates with SR-DRMs and are fully functional. Depletion of cholesterol caused the disruption of SR-DRMs.
Collapse
Affiliation(s)
- Chunlei Li
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, PR China
| | | | | | | |
Collapse
|
43
|
Klammt C, Schwarz D, Fendler K, Haase W, Dötsch V, Bernhard F. Evaluation of detergents for the soluble expression of alpha-helical and beta-barrel-type integral membrane proteins by a preparative scale individual cell-free expression system. FEBS J 2006; 272:6024-38. [PMID: 16302967 DOI: 10.1111/j.1742-4658.2005.05002.x] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cell-free expression has become a highly promising tool for the fast and efficient production of integral membrane proteins. The proteins can be produced as precipitates that solubilize in mild detergents usually without any prior denaturation steps. Alternatively, membrane proteins can be synthesized in a soluble form by adding detergents to the cell-free system. However, the effects of a representative variety of detergents on the production, solubility and activity of a wider range of membrane proteins upon cell-free expression are currently unknown. We therefore analyzed the cell-free expression of three structurally very different membrane proteins, namely the bacterial alpha-helical multidrug transporter, EmrE, the beta-barrel nucleoside transporter, Tsx, and the porcine vasopressin receptor of the eukaryotic superfamily of G-protein coupled receptors. All three membrane proteins could be produced in amounts of several mg per one ml of reaction mixture. In general, the detergent 1-myristoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] was found to be most effective for the resolubilization of membrane protein precipitates, while long chain polyoxyethylene-alkyl-ethers proved to be most suitable for the soluble expression of all three types of membrane proteins. The yield of soluble expressed membrane protein remained relatively stable above a certain threshold concentration of the detergents. We report, for the first time, the high-level cell-free expression of a beta-barrel type membrane protein in a functional form. Structural and functional variations of the analyzed membrane proteins are evident that correspond with the mode of expression and that depend on the supplied detergent.
Collapse
Affiliation(s)
- Christian Klammt
- Centre for Biomolecular Magnetic Resonance, University of Frankfurt/Main, Institute for Biophysical Chemistry, Frankfurt/Main, Germany
| | | | | | | | | | | |
Collapse
|
44
|
Mandal A, Das S, Chakraborti T, Kar P, Ghosh B, Chakraborti S. Solubilization, purification and reconstitution of Ca2+-ATPase from bovine pulmonary artery smooth muscle microsomes by different detergents: Preservation of native structure and function of the enzyme by DHPC. Biochim Biophys Acta Gen Subj 2006; 1760:20-31. [PMID: 16278046 DOI: 10.1016/j.bbagen.2005.09.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Revised: 09/21/2005] [Accepted: 09/27/2005] [Indexed: 10/25/2022]
Abstract
The properties of Ca(2+)-ATPase purified and reconstituted from bovine pulmonary artery smooth muscle microsomes {enriched with endoplasmic reticulum (ER)} were studied using the detergents 1,2-diheptanoyl-sn-phosphatidylcholine (DHPC), poly(oxy-ethylene)8-lauryl ether (C(12)E(8)) and Triton X-100 as the solubilizing agents. Solubilization with DHPC consistently gave higher yields of purified Ca(2+)-ATPase with a greater specific activity than solubilization with C(12)E(8) or Triton X-100. DHPC was determined to be superior to C(12)E(8); while that the C(12)E(8) was determined to be better than Triton X-100 in active enzyme yields and specific activity. DHPC solubilized and purified Ca(2+)-ATPase retained the E1Ca-E1*Ca conformational transition as that observed for native microsomes; whereas the C(12)E(8) and Triton X-100 solubilized preparations did not fully retain this transition. The coupling of Ca(2+) transported to ATP hydrolyzed in the DHPC purified enzyme reconstituted in liposomes was similar to that of the native micosomes, whereas that the coupling was much lower for the C(12)E(8) and Triton X-100 purified enzyme reconstituted in liposomes. The specific activity of Ca(2+)-ATPase reconstituted into dioleoyl-phosphatidylcholine (DOPC) vesicles with DHPC was 2.5-fold and 3-fold greater than that achieved with C(12)E(8) and Triton X-100, respectively. Addition of the protonophore, FCCP caused a marked increase in Ca(2+) uptake in the reconstituted proteoliposomes compared with the untreated liposomes. Circular dichroism analysis of the three detergents solubilized and purified enzyme preparations showed that the increased negative ellipticity at 223 nm is well correlated with decreased specific activity. It, therefore, appears that the DHPC purified Ca(2+)-ATPase retained more organized and native secondary conformation compared to C(12)E(8) and Triton X-100 solubilized and purified preparations. The size distribution of the reconstituted liposomes measured by quasi-elastic light scattering indicated that DHPC preparation has nearly similar size to that of the native microsomal vesicles whereas C(12)E(8) and Triton X-100 preparations have to some extent smaller size. These studies suggest that the Ca(2+)-ATPase solubilized, purified and reconstituted with DHPC is superior to that obtained with C(12)E(8) and Triton X-100 in many ways, which is suitable for detailed studies on the mechanism of ion transport and the role of protein-lipid interactions in the function of the membrane-bound enzyme.
Collapse
Affiliation(s)
- Amritlal Mandal
- Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal, India
| | | | | | | | | | | |
Collapse
|
45
|
Killig F, Stark G, Apell HJ. Photodynamic inactivation of the Na,K-ATPase occurs via different pathways. J Membr Biol 2005; 200:133-44. [PMID: 15625822 DOI: 10.1007/s00232-004-0700-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The photodynamic, i.e., the light-induced, inactivation of the Na,K-ATPase in the presence of the sensitizer rose bengal was studied under different conditions. The shape of inactivation curves of the enzyme activity was analyzed as well as partial reactions of the pump cycle. Both experimental approaches showed the existence of two different time constants of inactivation of the ion pump, which reflect two pathways of a photodynamic modification. This is supported by the following observations: (1) The amplitude of the initial fast decay of enzyme activity was enhanced in the presence of D2O and reduced in the presence of the singlet oxygen scavenger imidazole. (Similar results were found for the SR Ca-ATPase.) (2) Contrary to the fast enzyme inactivation the slow process shows an inverse dose-rate behavior. (3) Inactivation of the partial reactions of Na+ -binding and of K+-binding to the membrane domain of the Na,K-ATPase showed only a single time constant, which corresponded to the slower time constant of enzyme inactivation. In the presence of high concentrations of singlet oxygen the fast time constant dominated the inactivation of the ATP-induced partial reaction for which the cytoplasmic domains of the enzyme play an important role. The data support the conclusion that fast inactivation is due to modification of the cytoplasmic domains and slow inactivation due to modifications of the membrane domain of the ion pumps.
Collapse
Affiliation(s)
- F Killig
- Department of Biology, University of Konstanz, Konstanz, Germany
| | | | | |
Collapse
|
46
|
Girard P, Pécréaux J, Lenoir G, Falson P, Rigaud JL, Bassereau P. A new method for the reconstitution of membrane proteins into giant unilamellar vesicles. Biophys J 2005; 87:419-29. [PMID: 15240476 PMCID: PMC1304363 DOI: 10.1529/biophysj.104.040360] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In this work, we have investigated a new and general method for the reconstitution of membrane proteins into giant unilamellar vesicles (GUVs). We have analyzed systematically the reconstitution of two radically different membrane proteins, the sarcoplasmic reticulum Ca(2+)-ATPase and the H(+) pump bacteriorhodopsin. In a first step, our method involved a detergent-mediated reconstitution of solubilized membrane proteins into proteoliposomes of 0.1-0.2 microm in size. In a second step, these preformed proteoliposomes were partially dried under controlled humidity followed, in a third step, by electroswelling of the partially dried film to give GUVs. The physical characteristics of GUVs were analyzed in terms of morphology, size, and lamellarity using phase-contrast and differential interference contrast microscopy. The reconstitution process was further characterized by analyzing protein incorporation and biological activity. Both membrane proteins could be homogeneously incorporated into GUVs at lipid/protein ratios ranging from 5 to 40 (w/w). After reconstitution, both proteins retained their biological activity as demonstrated by H(+) or Ca(2+) pumping driven by bacteriorhodopsin or Ca(2+)-ATPase, respectively. This constitutes an efficient new method of reconstitution, leading to the production of large unilamellar membrane protein-containing vesicles of more than 20 microm in diameter, which should prove useful for functional and structural studies through the use of optical microscopy, optical tweezers, microelectrodes, or atomic force microscopy.
Collapse
Affiliation(s)
- Philippe Girard
- Laboratoire [corrected] Physico Chimie Cioue, Unité Mixte de Recherche 168 Centre National de la Recherche Scientifique/Institut Curie, 75231 Paris Cedex 05, France.
| | | | | | | | | | | |
Collapse
|
47
|
Seddon AM, Curnow P, Booth PJ. Membrane proteins, lipids and detergents: not just a soap opera. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1666:105-17. [PMID: 15519311 DOI: 10.1016/j.bbamem.2004.04.011] [Citation(s) in RCA: 904] [Impact Index Per Article: 45.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Accepted: 04/29/2004] [Indexed: 11/30/2022]
Abstract
Studying membrane proteins represents a major challenge in protein biochemistry, with one of the major difficulties being the problems encountered when working outside the natural lipid environment. In vitro studies such as crystallization are reliant on the successful solubilization or reconstitution of membrane proteins, which generally involves the careful selection of solubilizing detergents and mixed lipid/detergent systems. This review will concentrate on the methods currently available for efficient reconstitution and solubilization of membrane proteins through the use of detergent micelles, mixed lipid/detergent micelles and bicelles or liposomes. We focus on the relevant molecular properties of the detergents and lipids that aid understanding of these processes. A significant barrier to membrane protein research is retaining the stability and function of the protein during solubilization, reconstitution and crystallization. We highlight some of the lessons learnt from studies of membrane protein folding in vitro and give an overview of the role that lipids can play in stabilizing the proteins.
Collapse
Affiliation(s)
- Annela M Seddon
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | | | | |
Collapse
|
48
|
Abstract
Tissue factor (TF), the physiological trigger of the blood clotting cascade, is also the active ingredient in thromboplastin preparations which are widely used in clotting assays such as the prothrombin time (PT) test. A type I integral membrane protein, TF must be incorporated into suitable phospholipid membranes for full procoagulant activity. Several methods exist for incorporating TF into phospholipid vesicles, typically employing the formation of mixed micelles containing detergent, phospholipid and TF, followed by detergent removal or dilution below the critical micelle concentration (CMC). These methods have certain drawbacks: they may take several days to complete, employ expensive detergents, are difficult to scale up, and do not always result in complete detergent removal. In this study we have investigated the use of a variety of detergents [Triton X-100, octaethylene glycol monododecyl ether (C(12)E(8)), cholate, deoxycholate, and n-octyl-beta-D-glucopyranoside], and the use of adsorbent beads (Bio-Beads SM-2) for removing detergent, in processes to incorporate TF into proteoliposomes with high specific activity in coagulation assays. The method we have developed is rapid and readily scalable, yielding thromboplastin preparations with specific activities in plasma clotting assays that are at least as high as those made with detergent dialysis.
Collapse
Affiliation(s)
- S A Smith
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | | |
Collapse
|
49
|
Affiliation(s)
- Jean-Louis Rigaud
- Institut Curie, UMR-CNRS 168 and LRC-CEA 34V, 11 Rue Pierre et Marie Curie, 75231 Paris, France
| | | |
Collapse
|
50
|
Affiliation(s)
- Rolf Schubert
- Pharmazeutisches Institut, Lehrstuhl für Pharmazeutische Technologie, Albert-Ludwigs-Universität-Freiburg, Hermann-herder Strasse 9, D-79104 Freiburg, Germany
| |
Collapse
|