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Brown KA, Gugger MK, Roberts DS, Moreno D, Chae PS, Ge Y, Jin S. Synthesis, Self-Assembly Properties, and Degradation Characterization of a Nonionic Photocleavable Azo-Sulfide Surfactant Family. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:1465-1473. [PMID: 36638323 PMCID: PMC10164600 DOI: 10.1021/acs.langmuir.2c02820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
We report the synthesis and characterization of a new family of maltose-derived nonionic surfactants that contain a photocleavable azo-sulfide linker (mAzo). The self-assembly properties of these surfactants were investigated using surface tension measurements to determine the critical micelle concentration (CMC), dynamic light scattering (DLS) to reveal the hydrodynamic radius of their self-assemblies, and transmission electron microscopy (TEM) to elucidate the micelle morphology. Ultraviolet-visible (UV-visible) spectroscopy confirmed the rapid photodegradation of these surfactants, but surface tension measurements of the surfactant solutions before and after degradation showed unusual degradation products. The photodegradation process was further studied using online liquid chromatography coupled with mass spectrometry (LC-MS),which revealed that these surfactants can form another photo-stable surfactant post-degradation. Finally, traditionally challenging proteins from heart tissue were solubilized using the mAzo surfactants to demonstrate their potential in biological applications.
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Affiliation(s)
- Kyle A. Brown
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
- Department of Surgery, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Morgan K. Gugger
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - David S. Roberts
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - David Moreno
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Pil Seok Chae
- Department of Bionano Engineering, Hanyang University, Ansan, 15588, South Korea
| | - Ying Ge
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
- Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
| | - Song Jin
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
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Luo W, Yang M, Zhao Y, Wang H, Yang X, Zhang W, Zhao F, Zhao S, Tao H. Transition-Linker Containing Detergents for Membrane Protein Studies. Chemistry 2022; 28:e202202242. [PMID: 36053145 DOI: 10.1002/chem.202202242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Indexed: 12/14/2022]
Abstract
It is a pressing need, but still challenging to explore the structure and function of membrane proteins (MPs). One of the main obstacles is the limited availability of matched detergents for the handling of specific MPs. We describe herein the design of new detergents by incorporation of a transition linker between the hydrophilic head and the hydrophobic tail. This design allows a gradual change of hydrophobicity between the outside and inside of micelles, in contrast to the abrupt switch in conventional detergents. Notably, many of these detergents assembled into micelles in while retaining low critical micelle concentrations. Meanwhile, thermal stabilizing evaluation identified superior detergents for representative MPs, including G protein-coupled receptors and a transporter protein. Among them, further improved the NMR study of MPs. We anticipate these that results will encourage future detergent expansion through new remodeling on the traditional detergent scaffold.
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Affiliation(s)
- Weiling Luo
- Shanghai Frontiers Science Center of TCM Chemical Biology, Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, 201203, Shanghai, P. R. China.,iHuman Institute, ShanghaiTech University, 201210, Shanghai, P. R. China.,School of Life Science and Technology, ShanghaiTech University, 201210, Shanghai, P. R. China
| | - Meifang Yang
- Shanghai Frontiers Science Center of TCM Chemical Biology, Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, 201203, Shanghai, P. R. China
| | - Yitian Zhao
- Shanghai Frontiers Science Center of TCM Chemical Biology, Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, 201203, Shanghai, P. R. China
| | - Huixia Wang
- iHuman Institute, ShanghaiTech University, 201210, Shanghai, P. R. China
| | - Xiaodi Yang
- Shanghai Frontiers Science Center of TCM Chemical Biology, Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, 201203, Shanghai, P. R. China
| | - Wei Zhang
- College of Chemistry and Materials Science, Hebei Normal University, 050024, Shijiazhuang, P. R. China
| | - Fei Zhao
- iHuman Institute, ShanghaiTech University, 201210, Shanghai, P. R. China
| | - Suwen Zhao
- iHuman Institute, ShanghaiTech University, 201210, Shanghai, P. R. China.,School of Life Science and Technology, ShanghaiTech University, 201210, Shanghai, P. R. China
| | - Houchao Tao
- Shanghai Frontiers Science Center of TCM Chemical Biology, Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, 201203, Shanghai, P. R. China
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Ahangama Liyanage L, Harris MS, Cook GA. In Vitro Glycosylation of Membrane Proteins Using N-Glycosyltransferase. ACS OMEGA 2021; 6:12133-12142. [PMID: 34056367 PMCID: PMC8154143 DOI: 10.1021/acsomega.1c00835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 04/08/2021] [Indexed: 06/12/2023]
Abstract
Glycoproteins are post-translationally modified proteins that take part in nearly every biological process and make up a large percent of the proteome. N-Linked glycosylation can be performed by N-glycosyltransferase (NGT), which recognizes the consensus amino acid sequence, -Asn-X-Ser/Thr- (NXT), within the protein. The enzyme catalyzes glycosidic bond formation between the oligosaccharide donor, containing nucleoside phosphatase, and the amide nitrogen of the asparagine residue. The attachment of the sugar moiety can influence physiological and biological properties of the protein by affecting their folding, modulating interactions with other biomolecules, and modifying their functions at the cellular level. We are specifically interested in the properties of membrane glycoproteins, which are key components in a number of different disease states. Therefore, the use of in vitro protein glycosylation can help further evaluate the effects of the properties for these important macromolecules. In vitro studies of N-linked glycosylation were done in a stepwise fashion in a membrane-mimetic environment to confirm that the methods for glycosylating soluble proteins could be applicable to membrane proteins. Detergent and lipid systems were used since hydrophobic peptides and membrane proteins are insoluble in aqueous solvents. The stepwise method consisted of the glycosylation of a soluble 7-residue peptide, a hydrophobic WALP-NVT peptide, and a γ-sarcoglycan membrane protein, all of which contained the glycosylation site Asn-Val-Thr (NVT). Glycosylation of the samples was performed using Escherichia coli-expressed NGT from the Actinobacillus pleuropneumoniae genome, and a single sugar moiety of glucose, provided from a nucleotide-linked donor, was added to the glycosylation site. Gel electrophoresis, mass spectrometry, and NMR studies were used for the detection of glycosyltransferase activity and to show the attachment of a single glucose molecule. Our experiments demonstrated that small or large membrane proteins that contain an N-glycosylation consensus sequence can be glycosylated by NGT in membrane-mimetic environments.
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The LeuT-fold neurotransmitter:sodium symporter MhsT has two substrate sites. Proc Natl Acad Sci U S A 2018; 115:E7924-E7931. [PMID: 30082383 DOI: 10.1073/pnas.1717444115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Crystal structures of the neurotransmitter:sodium symporter MhsT revealed occluded inward-facing states with one substrate (Trp) bound in the primary substrate (S1) site and a collapsed extracellular vestibule, which in LeuT contains the second substrate (S2) site. In n-dodecyl-β-d-maltoside, the detergent used to prepare MhsT for crystallization, the substrate-to-protein binding stoichiometry was determined by using scintillation proximity to be 1 Trp:MhsT. Here, using the same experimental approach, as well as equilibrium dialysis, we report that in n-decyl-β-d-maltoside, or after reconstitution in lipid, MhsT, like LeuT, can simultaneously bind two Trp substrate molecules. Trp binding to the S2 site sterically blocks access to a substituted Cys at position 33 in the S2 site, as well as access to the deeper S1 site. Mutation of either the S1 or S2 site disrupts transport, consistent with previous studies in LeuT showing that substrate binding to the S2 site is an essential component of the transport mechanism.
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Mio K, Sato C. Lipid environment of membrane proteins in cryo-EM based structural analysis. Biophys Rev 2018; 10:307-316. [PMID: 29256118 PMCID: PMC5899730 DOI: 10.1007/s12551-017-0371-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/20/2017] [Indexed: 12/18/2022] Open
Abstract
Cryoelectron microscopy (cryo-EM) in association with a single particle analysis method (SPA) is now a promising tool to determine the structures of proteins and their macromolecular complexes. The development of direct electron detection cameras and image processing technologies has allowed the structures of many important proteins to be solved at near-atomic resolution or, in some cases, at atomic resolution, by overcoming difficulties in crystallization or low yield of protein production. In the case of membrane-integrated proteins, the proteins were traditionally solubilized and stabilized with various kind of detergents. However, the density of detergent micelles diminished the contrast of membrane proteins in cryo-EM studies and made it difficult to obtain high-resolution structures. To improve the resolution of membrane protein structures in cryo-EM studies, major improvements have been made both in sample preparation techniques and in hardware and software developments. The focus of our review is on improvements which have been made in the various techniques for sample preparation for cryo-EM studies, with a specific interest placed on techniques for mimicking the lipid environment of membrane proteins.
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Affiliation(s)
- Kazuhiro Mio
- AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory (OPERANDO-OIL), National Institute of Advanced Industrial Science and Technology (AIST), Chiba, 277-8568, Japan.
- Molecular Profiling Research Center for Drug Discovery (molprof), National Institute of Advanced Industrial Science and Technology (AIST), Tokyo, 135-0064, Japan.
| | - Chikara Sato
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan.
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6
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Liposome-supported enzymatic peritoneal dialysis. Biomaterials 2017; 145:128-137. [DOI: 10.1016/j.biomaterials.2017.08.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 08/08/2017] [Accepted: 08/14/2017] [Indexed: 11/19/2022]
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Hybrid integrated biological-solid-state system powered with adenosine triphosphate. Nat Commun 2015; 6:10070. [PMID: 26638983 PMCID: PMC4686768 DOI: 10.1038/ncomms10070] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 10/27/2015] [Indexed: 11/17/2022] Open
Abstract
There is enormous potential in combining the capabilities of the biological and the solid state to create hybrid engineered systems. While there have been recent efforts to harness power from naturally occurring potentials in living systems in plants and animals to power complementary metal-oxide-semiconductor integrated circuits, here we report the first successful effort to isolate the energetics of an electrogenic ion pump in an engineered in vitro environment to power such an artificial system. An integrated circuit is powered by adenosine triphosphate through the action of Na+/K+ adenosine triphosphatases in an integrated in vitro lipid bilayer membrane. The ion pumps (active in the membrane at numbers exceeding 2 × 106 mm−2) are able to sustain a short-circuit current of 32.6 pA mm−2 and an open-circuit voltage of 78 mV, providing for a maximum power transfer of 1.27 pW mm−2 from a single bilayer. Two series-stacked bilayers provide a voltage sufficient to operate an integrated circuit with a conversion efficiency of chemical to electrical energy of 14.9%. There is enormous potential in combining the capabilities of the biological and the solid-state to create hybrid engineered systems. Here, the authors develop a technique to incorporate and activate ATPases in in vitro membranes to produce energy-harvestable currents to power an integrated circuit.
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Rather MY, Nordberg Karlsson E, Adlercreutz P. Complexation of alkyl glycosides with α-cyclodextrin can have drastically different effects on their conversion by glycoside hydrolases. J Biotechnol 2015; 200:52-8. [PMID: 25711178 DOI: 10.1016/j.jbiotec.2015.02.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 02/11/2015] [Accepted: 02/13/2015] [Indexed: 11/16/2022]
Abstract
Substrates present in aggregated forms, such as micelles, are often poorly converted by enzymes. Alkyl glycosides constitute typical examples and the critical micelle concentration (CMC) decreases with increasing length of the alkyl group. In this study, possibilities to hydrolyse alkyl glycosides by glycoside hydrolases were explored, and α-cyclodextrin was used as an agent to form inclusion complexes with the alkyl glycosides, thereby preventing micelle formation. The cyclodextrin complexes were accepted as substrates by the enzymes to variable extent. The β-glucosidases originating from Thermotoga neapolitana (Tn Bgl3B) and from almond were not at all able to hydrolyse alkyl β-glucosides in the presence of 100mM α-cyclodextrin. However, Aspergillus niger amyloglucosidase readily accepted the complexes as substrates. In reactions involving decyl and dodecyl maltosides, the presence of 100mM α-cyclodextrin caused an increase in reaction rate in most cases, especially at high substrate concentrations. Surprisingly, the amyloglucosidase-catalyzed hydrolysis of octyl-β-maltoside to glucose and β-octylglucoside was faster in the presence of α-cyclodextrin than without, even at substrate concentrations below CMC. A possible explanation of the observed rate enhancement is that binding sites on the carbohydrate binding domain of amyloglucosidase, known to bind cyclodextrins, help to guide the alkyl glycoside-cyclodextrin complex to the active site, and thereby promote its conversion.
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Affiliation(s)
- Mohd Younis Rather
- Department of Biotechnology, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | | | - Patrick Adlercreutz
- Department of Biotechnology, Lund University, P.O. Box 124, SE-22100 Lund, Sweden.
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Cardoso MVC, Sabadini E. Before and beyond the micellization of n-alkyl glycosides. A water-1H NMR relaxation study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:15778-15786. [PMID: 24308316 DOI: 10.1021/la403526w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The interactions between the headgroups of n-alkyl glycoside (AG) and water molecules were studied by nuclear magnetic transverse relaxation times (T2) of the water protons before and beyond the micellization. Despite the low concentration of the surfactants (mM), their micellization induce strong effect on the T2 values of bulk water when the AG molecules self-aggregate into micelles. This is associated with the decreasing of the fraction of OH headgroups of AG to exchange protons with water molecules due to the OH headgroups intermolecular interactions of AG at the micelle surface. These findings support the computational results described in the literature, which indicate that the water hydrogen bonding to OH headgroups is perturbed at AG micelle surfaces.
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Affiliation(s)
- Marcus V C Cardoso
- Department of Physical Chemistry, Institute of Chemistry, University of Campinas - UNICAMP . P.O. Box 6154, 13084-862, Campinas, SP, Brazil
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Oliver RC, Lipfert J, Fox DA, Lo RH, Doniach S, Columbus L. Dependence of micelle size and shape on detergent alkyl chain length and head group. PLoS One 2013; 8:e62488. [PMID: 23667481 PMCID: PMC3648574 DOI: 10.1371/journal.pone.0062488] [Citation(s) in RCA: 161] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 03/20/2013] [Indexed: 11/19/2022] Open
Abstract
Micelle-forming detergents provide an amphipathic environment that can mimic lipid bilayers and are important tools for solubilizing membrane proteins for functional and structural investigations in vitro. However, the formation of a soluble protein-detergent complex (PDC) currently relies on empirical screening of detergents, and a stable and functional PDC is often not obtained. To provide a foundation for systematic comparisons between the properties of the detergent micelle and the resulting PDC, a comprehensive set of detergents commonly used for membrane protein studies are systematically investigated. Using small-angle X-ray scattering (SAXS), micelle shapes and sizes are determined for phosphocholines with 10, 12, and 14 alkyl carbons, glucosides with 8, 9, and 10 alkyl carbons, maltosides with 8, 10, and 12 alkyl carbons, and lysophosphatidyl glycerols with 14 and 16 alkyl carbons. The SAXS profiles are well described by two-component ellipsoid models, with an electron rich outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core composed of the alkyl chains. The minor axis of the elliptical micelle core from these models is constrained by the length of the alkyl chain, and increases by 1.2-1.5 Å per carbon addition to the alkyl chain. The major elliptical axis also increases with chain length; however, the ellipticity remains approximately constant for each detergent series. In addition, the aggregation number of these detergents increases by ∼16 monomers per micelle for each alkyl carbon added. The data provide a comprehensive view of the determinants of micelle shape and size and provide a baseline for correlating micelle properties with protein-detergent interactions.
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Affiliation(s)
- Ryan C. Oliver
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Jan Lipfert
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Daniel A. Fox
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Ryan H. Lo
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Sebastian Doniach
- Departments of Physics and Applied Physics, Biophysics Program, Stanford, California, United States of America
- Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California, United States of America
| | - Linda Columbus
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
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Haferkamp I, Linka N. Functional expression and characterisation of membrane transport proteins. PLANT BIOLOGY (STUTTGART, GERMANY) 2012; 14:675-90. [PMID: 22639981 DOI: 10.1111/j.1438-8677.2012.00591.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Membrane transporters set the framework organising the complexity of plant metabolism in cells, tissues and organisms. Their substrate specificity and controlled activity in different cells is a crucial part for plant metabolism to run pathways in concert. Transport proteins catalyse the uptake and exchange of ions, substrates, intermediates, products and cofactors across membranes. Given the large number of metabolites, a wide spectrum of transporters is required. The vast majority of in silico annotated membrane transporters in plant genomes, however, has not yet been functionally characterised. Hence, to understand the metabolic network as a whole, it is important to understand how transporters connect and control the metabolic pathways of plant cells. Heterologous expression and in vitro activity studies of recombinant transport proteins have highly improved their functional analysis in the last two decades. This review provides a comprehensive overview of the recent advances in membrane protein expression and functional characterisation using various host systems and transport assays.
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Affiliation(s)
- I Haferkamp
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - N Linka
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
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12
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Pramanik A, Zhang F, Schwarz H, Schreiber F, Braun V. ExbB Protein in the Cytoplasmic Membrane of Escherichia coli Forms a Stable Oligomer. Biochemistry 2010; 49:8721-8. [DOI: 10.1021/bi101143y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Avijit Pramanik
- Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Fajun Zhang
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morganstelle 10, 72076 Tübingen, Germany
| | - Heinz Schwarz
- Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Frank Schreiber
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morganstelle 10, 72076 Tübingen, Germany
| | - Volkmar Braun
- Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
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Maslennikov I, Kefala G, Johnson C, Riek R, Choe S, Kwiatkowski W. NMR spectroscopic and analytical ultracentrifuge analysis of membrane protein detergent complexes. BMC STRUCTURAL BIOLOGY 2007; 7:74. [PMID: 17988403 PMCID: PMC2219997 DOI: 10.1186/1472-6807-7-74] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 11/08/2007] [Indexed: 11/10/2022]
Abstract
BACKGROUND Structural studies of integral membrane proteins (IMPs) are hampered by inherent difficulties in their heterologous expression and in the purification of solubilized protein-detergent complexes (PDCs). The choice and concentrations of detergents used in an IMP preparation play a critical role in protein homogeneity and are thus important for successful crystallization. RESULTS Seeking an effective and standardized means applicable to genomic approaches for the characterization of PDCs, we chose 1D-NMR spectroscopic analysis to monitor the detergent content throughout their purification: protein extraction, detergent exchange, and sample concentration. We demonstrate that a single NMR measurement combined with a SDS-PAGE of a detergent extracted sample provides a useful gauge of the detergent's extraction potential for a given protein. Furthermore, careful monitoring of the detergent content during the process of IMP production allows for a high level of reproducibility. We also show that in many cases a simple sedimentation velocity measurement provides sufficient data to estimate both the oligomeric state and the detergent-to-protein ratio in PDCs, as well as to evaluate the homogeneity of the samples prior to crystallization screening. CONCLUSION The techniques presented here facilitate the screening and selection of the extraction detergent, as well as help to maintain reproducibility in the detergent exchange and PDC concentration procedures. Such reproducibility is particularly important for the optimization of initial crystallization conditions, for which multiple purifications are routinely required.
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Affiliation(s)
- Innokentiy Maslennikov
- Structural Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Rd., La Jolla, CA 92037, USA.
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Stimac R, Kerek F, Apell HJ. Mechanism of the Na,K-ATPase Inhibition by MCS Derivatives. J Membr Biol 2005; 205:89-101. [PMID: 16283589 DOI: 10.1007/s00232-005-0767-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 08/18/2005] [Indexed: 10/25/2022]
Abstract
The previously reported class of potent inorganic inhibitors of Na,K-ATPase, named MCS factors, was shown to inhibit not only Na,K-ATPase but several P-type ATPases with high potency in the sub-micromolar range. These MCS factors were found to bind to the intracellular side of the Na, K-ATPase. The inhibition is not competitive with ouabain binding, thus excluding its role as cardiac-steroid-like inhibitor of the Na,K-ATPase. The mechanism of inhibition of Na,K-ATPase was investigated with the fluorescent styryl dye RH421, a dye known to report changes of local electric fields in the membrane dielectric. MCS factors interact with the Na,K-ATPase in the E(1) conformation of the ion pump and induce a conformational rearrangement that causes a change of the equilibrium dissociation constant for one of the first two intracellular cation binding sites. The MCS-inhibited state was found to have bound one cation (H(+), Na(+) or K(+)) in one of the two unspecific binding sites, and at high Na(+) concentrations another Na(+) ion was bound to the highly Na(+)-selective ion-binding site.
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Affiliation(s)
- R Stimac
- Department of Biology, University of Konstanz, Konstanz, Germany
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15
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Apell HJ. Separation and characterization of Na+,K(+)-ATPase containing vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1196:29-37. [PMID: 7986807 DOI: 10.1016/0005-2736(94)90291-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Na+,K(+)-ATPase was reconstituted in vesicles prepared by a dialysis method. Ion-exchange chromatography was used to obtain well characterized fractions from the inhomogeneous vesicle preparation. Lipid and protein content was determined by optical methods during the elution process. It was possible to separate fractions with distinct enzymatic and transport activities. A protocol was set up, which allowed to calculate the average number of 5-IAF labeled ion pumps per vesicle in the different fractions. The dependence of the number of protein molecules per vesicle was studied as function of the initial protein concentration added to the lipid solution before dialysis. The transport activity disappears completely at very low protein concentrations (3.3 micrograms protein per mg lipid). This observation is in favor of the proposal discussed in the literature, that the heterodimer (alpha beta)2 is the transport-active form of the Na+,K(+)-ATPase. The presented method can be applied to all reconstituted vesicle preparations in which the proteins can be labeled quantitatively with a fluorescence dye.
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16
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Riek R, Apell HJ. Investigation of reconstitution of the Na, K-ATPase in lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1148:321-30. [PMID: 8389199 DOI: 10.1016/0005-2736(93)90146-q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Vesicles containing Na,K-ATPase were prepared by a dialysis method in buffers with various concentrations of K+ and Na+ ions. Ion-exchange chromatography has been used to separate proteoliposomes into protein-depleted and protein-rich fractions. The pumping activity of reconstituted ion pumps has been determined in the different fractions of the vesicle preparation using voltage-dependent fluorescence dyes. This method allowed to characterise vesicle fractions by a quantity which is proportional to the average number of pumps per vesicle with an active (inside-out) orientation. It could be shown that both, the amount of enzymatic active protein and the orientation of Na,K-ATPase in the vesicle lipid bilayer, is partially controlled by the Na+ and K+ concentration in the buffer during vesicle formation. High Na+ concentrations preferentially maintain the E1 conformation of the enzyme, which is less stable against denaturation during the dialysis, but displays a higher percentage of inside-out orientation of the transport-active protein. High K+ concentrations maintain the E2 conformation of the enzyme, which is stable against denaturation during the dialysis, but leads to a random orientation of the pump during dialysis.
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17
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Cornelius F. Functional reconstitution of the sodium pump. Kinetics of exchange reactions performed by reconstituted Na/K-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1071:19-66. [PMID: 1848452 DOI: 10.1016/0304-4157(91)90011-k] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- F Cornelius
- Institute of Biophysics, University of Aarhus, Denmark
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Villalobo A. Reconstitution of ion-motive transport ATPases in artificial lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1017:1-48. [PMID: 1693288 DOI: 10.1016/0005-2728(90)90176-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- A Villalobo
- Instituto de Investigaciones Biomédicas, C.S.I.C., Madrid, Spain
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Affiliation(s)
- H J Apell
- Department of Biology, University of Konstanz, Federal Republic of Germany
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