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A Procedure for Estimating the Absolute Potential Difference Across Metal|Water Interfaces: a Reassessment. J Electroanal Chem (Lausanne) 2022. [DOI: 10.1016/j.jelechem.2022.116500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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2
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Guidelli R, Becucci L. Functional activity of peptide ion channels in tethered bilayer lipid membranes: Review. ELECTROCHEMICAL SCIENCE ADVANCES 2021. [DOI: 10.1002/elsa.202100180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Rolando Guidelli
- Department of Chemistry University of Florence Sesto Fiorentino Firenze Italy
| | - Lucia Becucci
- Ministero dell'Istruzione Scuola Media “Guglielmo Marconi” San Giovanni Valdarno Arezzo Italy
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3
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Köhler S, Fragneto G, Alcaraz JP, Nelson A, Martin DK, Maccarini M. Nanostructural Characterization of Cardiolipin-Containing Tethered Lipid Bilayers Adsorbed on Gold and Silicon Substrates for Protein Incorporation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:8908-8923. [PMID: 34286589 DOI: 10.1021/acs.langmuir.1c00119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A key to the development of lipid membrane-based devices is a fundamental understanding of how the molecular structure of the lipid bilayer membrane is influenced by the type of lipids used to build the membrane. This is particularly important when membrane proteins are included in these devices since the precise lipid environment affects the ability to incorporate membrane proteins and their functionality. Here, we used neutron reflectometry to investigate the structure of tethered bilayer lipid membranes and to characterize the incorporation of the NhaA sodium proton exchanger in the bilayer. The lipid membranes were composed of two lipids, dioleoyl phosphatidylcholine and cardiolipin, and were adsorbed on gold and silicon substrates using two different tethering architectures based on functionalized oligoethylene glycol molecules of different lengths. In all of the investigated samples, the addition of cardiolipin caused distinct structural rearrangement including crowding of ethylene glycol groups of the tethering molecules in the inner head region and a thinning of the lipid tail region. The incorporation of NhaA in the tethered bilayers following two different protocols is quantified, and the way protein incorporation modulates the structural properties of these membranes is detailed.
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Affiliation(s)
- Sebastian Köhler
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC/SyNaBi, 38000 Grenoble, France
- Institut Laue-Langevin, 38042 Grenoble, France
| | | | - Jean-Pierre Alcaraz
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC/SyNaBi, 38000 Grenoble, France
| | - Andrew Nelson
- ANSTO-Sydney, New Illawarra Road, Lucas Heights, NSW 2234, Australia
| | - Donald K Martin
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC/SyNaBi, 38000 Grenoble, France
| | - Marco Maccarini
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC/SyNaBi, 38000 Grenoble, France
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Cao Y, Yang R, Sun J, Zhang W, Lee I, Wang W, Meng X. Effects of amino acid modifications on the permeability of the pentameric sarcolipin channel. Proteins 2020; 89:427-435. [PMID: 33244801 DOI: 10.1002/prot.26028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 09/28/2020] [Accepted: 11/21/2020] [Indexed: 12/12/2022]
Abstract
Sarcolipin (SLN) is an important transmembrane (TM) protein encoded by long noncoding RNA. SLN is expressed in the sarcoplasmic reticulum and regulates cardiac and skeletal muscle contractions. SLN forms a pentameric hydrophobic ligand-gated ion channel. The protonation of Glu7 (protonated SLN, pSLN) and mutation of Thr18 to Ala18 (T18A) have been reported to exert a significant influence on the permeability of the channel. In this study, the altered permeability of both the pSLN and T18A pentameric channels was simulated. Combined with molecular dynamics simulation, the free-energy landscape for single ions, computational electrophysiology, diffusion coefficient, and pore geometrical characteristic analyses were performed to further understand the properties of amino acid modifications in the SLN pentameric channel. The results suggest that both the pSLN and T18A pentameric channels form stable hydrophobic ligand-gated channels. The TM voltage has a positive effect on the permeability of water molecules and ions. By using pSLN and T18A, our study provides helpful information on the pore-forming mechanism of SLN and furthers our understanding of the regulatory mechanisms underlying the permeation of ions and water molecules in the pentameric SLN channel.
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Affiliation(s)
- Yipeng Cao
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin's Clinical Research Center for Cancer, Tianjin, China.,National Supercomputer Center in Tianjin, TEDA - Tianjin Economic-Technological Development Area, Tianjin, China
| | - Rui Yang
- Department of Infection and Immunity, Tianjin Union Medical Center, Nankai University Affiliated Hospital, Tianjin, China
| | - Jiana Sun
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin's Clinical Research Center for Cancer, Tianjin, China
| | - Wenwen Zhang
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin's Clinical Research Center for Cancer, Tianjin, China
| | - Imshik Lee
- College of Physics, Nankai University, Tianjin, China
| | - Wei Wang
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin's Clinical Research Center for Cancer, Tianjin, China
| | - Xiangfei Meng
- National Supercomputer Center in Tianjin, TEDA - Tianjin Economic-Technological Development Area, Tianjin, China
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Glaves JP, Primeau JO, Gorski PA, Espinoza-Fonseca LM, Lemieux MJ, Young HS. Interaction of a Sarcolipin Pentamer and Monomer with the Sarcoplasmic Reticulum Calcium Pump, SERCA. Biophys J 2019; 118:518-531. [PMID: 31858977 DOI: 10.1016/j.bpj.2019.11.3385] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 10/30/2019] [Accepted: 11/18/2019] [Indexed: 11/27/2022] Open
Abstract
The sequential rise and fall of cytosolic calcium underlies the contraction-relaxation cycle of muscle cells. Whereas contraction is initiated by the release of calcium from the sarcoplasmic reticulum, muscle relaxation involves the active transport of calcium back into the sarcoplasmic reticulum. This reuptake of calcium is catalyzed by the sarcoendoplasmic reticulum Ca2+-ATPase (SERCA), which plays a lead role in muscle contractility. The activity of SERCA is regulated by small membrane protein subunits, the most well-known being phospholamban (PLN) and sarcolipin (SLN). SLN physically interacts with SERCA and differentially regulates contractility in skeletal and atrial muscle. SLN has also been implicated in skeletal muscle thermogenesis. Despite these important roles, the structural mechanisms by which SLN modulates SERCA-dependent contractility and thermogenesis remain unclear. Here, we functionally characterized wild-type SLN and a pair of mutants, Asn4-Ala and Thr5-Ala, which yielded gain-of-function behavior comparable to what has been found for PLN. Next, we analyzed two-dimensional crystals of SERCA in the presence of wild-type SLN by electron cryomicroscopy. The fundamental units of the crystals are antiparallel dimer ribbons of SERCA, known for decades as an assembly of calcium-free SERCA molecules induced by the addition of decavanadate. A projection map of the SERCA-SLN complex was determined to a resolution of 8.5 Å, which allowed the direct visualization of an SLN pentamer. The SLN pentamer was found to interact with transmembrane segment M3 of SERCA, although the interaction appeared to be indirect and mediated by an additional density consistent with an SLN monomer. This SERCA-SLN complex correlated with the ability of SLN to decrease the maximal activity of SERCA, which is distinct from the ability of PLN to increase the maximal activity of SLN. Protein-protein docking and molecular dynamics simulations provided models for the SLN pentamer and the novel interaction between SERCA and an SLN monomer.
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Affiliation(s)
- John Paul Glaves
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Joseph O Primeau
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Przemek A Gorski
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - L Michel Espinoza-Fonseca
- Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan
| | - M Joanne Lemieux
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Howard S Young
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
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7
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Espinoza-Fonseca LM. The Ca 2+-ATPase pump facilitates bidirectional proton transport across the sarco/endoplasmic reticulum. MOLECULAR BIOSYSTEMS 2017; 13:633-637. [PMID: 28290590 DOI: 10.1039/c7mb00065k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Ca2+ transport across the sarco/endoplasmic reticulum (SR) plays an essential role in intracellular Ca2+ homeostasis, signalling, cell differentiation and muscle contractility. During SR Ca2+ uptake and release, proton fluxes are required to balance the charge deficit generated by the exchange of Ca2+ and other ions across the SR. During Ca2+ uptake by the SR Ca2+-ATPase (SERCA), two protons are countertransported from the SR lumen to the cytosol, thus partially compensating for the charge moved by Ca2+ transport. Studies have shown that protons are also transported from the cytosol to the lumen during Ca2+ release, but a transporter that facilitates proton transport into the SR lumen has not been described. In this article we propose that SERCA forms pores that facilitate bidirectional proton transport across the SR. We describe the location and structure of water-filled pores in SERCA that form cytosolic and luminal pathways for protons to cross the SR membrane. Based on this structural information, we suggest mechanistic models for proton translocation to the cytosol during active Ca2+ transport, and into the SR lumen during SERCA inhibition by endogenous regulatory proteins. Finally, we discuss the physiological consequences of SERCA-mediated bidirectional proton transport across the SR membrane of muscle and non-muscle cells.
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Affiliation(s)
- L Michel Espinoza-Fonseca
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
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8
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Structure-Function Relationship of the SERCA Pump and Its Regulation by Phospholamban and Sarcolipin. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 981:77-119. [DOI: 10.1007/978-3-319-55858-5_5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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9
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Becucci L, Toppi A, Fiore A, Scaloni A, Guidelli R. Channel-forming activity of syringopeptin 25A in mercury-supported phospholipid monolayers and negatively charged bilayers. Bioelectrochemistry 2016; 111:131-42. [DOI: 10.1016/j.bioelechem.2016.06.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 06/10/2016] [Accepted: 06/12/2016] [Indexed: 11/15/2022]
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10
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Cao Y, Wu X, Wang X, Sun H, Lee I. Transmembrane dynamics of the Thr-5 phosphorylated sarcolipin pentameric channel. Arch Biochem Biophys 2016; 604:143-51. [PMID: 27378083 DOI: 10.1016/j.abb.2016.06.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Revised: 06/23/2016] [Accepted: 06/24/2016] [Indexed: 12/16/2022]
Abstract
Sarcolipin (SLN), an important membrane protein expressed in the sarcoplasmic reticulum (SR), regulates muscle contractions in cardiac and skeletal muscle. The phosphorylation at amino acid Thr5 of the SLN protein modulates the amount of Ca(2+) that passes through the SR. Using molecular dynamics simulation, we evaluated the phosphorylation at Thr5 of pentameric SLN (phospho-SLN) channel's energy barrier and pore characteristics by calculating the potential of mean force (PMF) along the channel pore and determining the diffusion coefficient. The results indicate that pentameric phospho-SLN promotes penetration of monovalent and divalent ions through the channel. The analysis of PMF, pore radius and diffusion coefficient indicates that Leu21 is the hydrophobic gate of the pentameric SLN channel. In the channel, water molecules near the Leu21 pore demonstrated a clear hydrated-dehydrated transition; however, the mutation of Leu21 to an Alanine (L21A) destroyed the hydrated-dehydrated transitions. These water-dynamic behaviors and PMF confirm that Leu21 is the key residue that regulates the ion permeability of the pentameric SLN channel. These results provide the structural-basis insights and molecular-dynamic information that are needed to understand the regulatory mechanisms of ion permeability in the pentameric SLN channel.
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Affiliation(s)
- Yipeng Cao
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China
| | - Xue Wu
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China
| | - Xinyu Wang
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China
| | - Haiying Sun
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China
| | - Imshik Lee
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China.
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11
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Cao Y, Wu X, Lee I, Wang X. Molecular dynamics of water and monovalent-ions transportation mechanisms of pentameric sarcolipin. Proteins 2015; 84:73-81. [DOI: 10.1002/prot.24956] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 10/16/2015] [Accepted: 10/19/2015] [Indexed: 12/15/2022]
Affiliation(s)
- Yipeng Cao
- Institute of Physics, Nankai University; Tianjin China
| | - Xue Wu
- Institute of Physics, Nankai University; Tianjin China
| | - Imshik Lee
- Institute of Physics, Nankai University; Tianjin China
| | - Xinyu Wang
- Institute of Physics, Nankai University; Tianjin China
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12
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Musgrove A, Bizzotto D. Potential Controls the Interaction of Liposomes with Octadecanol-Modified Au Electrodes: An in Situ AFM Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12797-12806. [PMID: 26528884 DOI: 10.1021/acs.langmuir.5b03605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The formation of supported lipid bilayers using liposomes requires interaction with the solid surface, rupture of the liposome, and spreading to cover the surface with a lipid bilayer. This can result in a less-than-uniform coating of the solid surface. Presented is a method that uses the electrochemical poration of an adsorbed lipid-like layer on a Au electrode to control the interaction of 100 nm DOPC liposomes. An octadecanol-coated Au-on-mica surface was imaged using tapping-mode AFM during the application of potential in the presence or absence of liposomes. When the substrate potential was made negative enough, defects formed in the adsorbed layer and new taller features were observed. More features were observed and existing features increased in size with time spent at this negative poration potential. The new features were 1.8-2.0 nm higher than the octadecanol-coated gold surface, half the thickness of a DOPC bilayer. These features were not observed in the absence of liposomes when undergoing the same potential perturbation. In the presence of liposomes, the application of a poration potential was needed to initiate the formation of these taller features. Once the applied potential was removed, the features stopped growing and no new regions were observed. The size of these new regions was consistent with the footprint of a flattened 100 nm liposome. It is speculated that the DOPC liposomes were able to interact with the defects and became soluble in the octadecanol, creating a taller region that was limited in size to the liposome that adsorbed and became incorporated. This AFM study confirms previous in situ fluorescence measurements of the same system and illustrates the use of a potential perturbation to control the formation of these regions of increased DOPC content.
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Affiliation(s)
- Amanda Musgrove
- AMPEL, Department of Chemistry, University of British Columbia , Vancouver, British Columbia V6T 1Z4, Canada
| | - Dan Bizzotto
- AMPEL, Department of Chemistry, University of British Columbia , Vancouver, British Columbia V6T 1Z4, Canada
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13
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Becucci L, Tramonti V, Fiore A, Fogliano V, Scaloni A, Guidelli R. Channel-forming activity of syringomycin E in two mercury-supported biomimetic membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:932-41. [DOI: 10.1016/j.bbamem.2014.12.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 12/05/2014] [Accepted: 12/08/2014] [Indexed: 10/24/2022]
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Becucci L, Foresti ML, Schwan A, Guidelli R. Can proton pumping by SERCA enhance the regulatory role of phospholamban and sarcolipin? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2682-90. [DOI: 10.1016/j.bbamem.2013.07.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 06/22/2013] [Accepted: 07/08/2013] [Indexed: 11/26/2022]
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Becucci L, Maran F, Guidelli R. Probing membrane permeabilization by the antibiotic lipopeptaibol trichogin GA IV in a tethered bilayer lipid membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1656-62. [DOI: 10.1016/j.bbamem.2012.03.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/16/2012] [Accepted: 03/30/2012] [Indexed: 10/28/2022]
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16
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Probing membrane permeabilization by the antimicrobial peptide distinctin in mercury-supported biomimetic membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2745-52. [DOI: 10.1016/j.bbamem.2011.07.033] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 06/27/2011] [Accepted: 07/21/2011] [Indexed: 02/01/2023]
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Autry JM, Rubin JE, Pietrini SD, Winters DL, Robia SL, Thomas DD. Oligomeric interactions of sarcolipin and the Ca-ATPase. J Biol Chem 2011; 286:31697-706. [PMID: 21737843 DOI: 10.1074/jbc.m111.246843] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have detected directly the interactions of sarcolipin (SLN) and the sarcoplasmic reticulum Ca-ATPase (SERCA) by measuring fluorescence resonance energy transfer (FRET) between fusion proteins labeled with cyan fluorescent protein (donor) and yellow fluorescent protein (acceptor). SLN is a membrane protein that helps control contractility by regulating SERCA activity in fast-twitch and atrial muscle. Here we used FRET microscopy and spectroscopy with baculovirus expression in insect cells to provide direct evidence for: 1) oligomerization of SLN and 2) regulatory complex formation between SLN and the fast-twitch muscle Ca-ATPase (SERCA1a isoform). FRET experiments demonstrated that SLN monomers self-associate into dimers and higher order oligomers in the absence of SERCA, and that SLN monomers also bind to SERCA monomers in a 1:1 binary complex when the two proteins are coexpressed. FRET experiments further demonstrated that the binding affinity of SLN for itself is similar to that for SERCA. Mutating SLN residue isoleucine-17 to alanine (I17A) decreased the binding affinity of SLN self-association and converted higher order oligomers into monomers and dimers. The I17A mutation also decreased SLN binding affinity for SERCA but maintained 1:1 stoichiometry in the regulatory complex. Thus, isoleucine-17 plays dual roles in determining the distribution of SLN homo-oligomers and stabilizing the formation of SERCA-SLN heterodimers. FRET results for SLN self-association were supported by the effects of SLN expression in bacterial cells. We propose that SLN exists as multiple molecular species in muscle, including SERCA-free (monomer, dimer, oligomer) and SERCA-bound (heterodimer), with transmembrane zipper residues of SLN serving to stabilize oligomeric interactions.
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Affiliation(s)
- Joseph M Autry
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Becucci L, D'Amico M, Cinotti S, Daniele S, Guidelli R. Tethered bilayer lipid micromembranes for single-channel recording: the role of adsorbed and partially fused lipid vesicles. Phys Chem Chem Phys 2011; 13:13341-8. [PMID: 21701758 DOI: 10.1039/c1cp20667b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mercury-supported bilayer lipid micromembrane was prepared by anchoring a thiolipid monolayer to a mercury cap electrodeposited on a platinum microdisc about 20 μm in diameter; a lipid monolayer was then self-assembled on top of the thiolipid monolayer either by vesicle fusion or by spilling a few drops of a lipid solution in chloroform on the cap and allowing the solvent to evaporate. Single-channel recording following incorporation of the alamethicin channel-forming peptide exhibits quite different features, depending on the procedure followed to form the distal lipid monolayer. The "spilling" procedure, which avoids the formation of adsorbed or partially fused vesicles, yields very sharp single-channel currents lasting only one or two milliseconds. These are ascribed to ionic flux into the hydrophilic spacer moiety of the thiolipid. Conversely, the vesicle-fusion procedure yields much longer single-channel openings analogous to those obtained with conventional bilayer lipid membranes, albeit smaller. This difference in behavior is explained by ascribing the latter single-channel currents to ionic flux into vesicles adsorbed and/or partially fused onto the tethered lipid bilayer, via capacitive coupling.
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Affiliation(s)
- Lucia Becucci
- Department of Chemistry, Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.
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Nullmeier M, Koliwer-Brandl H, Kelm S, Zägel P, Koch KW, Brand I. Impact of Strong and Weak Lipid-Protein Interactions on the Structure of a Lipid Bilayer on a Gold Electrode Surface. Chemphyschem 2011; 12:1066-79. [DOI: 10.1002/cphc.201100036] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 02/07/2011] [Indexed: 01/13/2023]
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20
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Nelson A. Electrochemistry of mercury supported phospholipid monolayers and bilayers. Curr Opin Colloid Interface Sci 2010. [DOI: 10.1016/j.cocis.2010.07.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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21
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Becucci L, Guidelli R, Karim CB, Thomas DD, Veglia G. The role of sarcolipin and ATP in the transport of phosphate ion into the sarcoplasmic reticulum. Biophys J 2010; 97:2693-9. [PMID: 19917222 DOI: 10.1016/j.bpj.2009.08.035] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 08/01/2009] [Accepted: 08/25/2009] [Indexed: 10/20/2022] Open
Abstract
In a previous study, sarcolipin (SLN) was shown to form channels selective toward chloride ion when incorporated in a mercury-supported tethered bilayer lipid membrane (tBLM). Its incorporation had only a modest permeabilizing effect on phosphate ion. In this note the resistance of a tBLM membrane incorporating sarcolipin was investigated by electrochemical impedance spectroscopy in aqueous solutions of 0.05 M sodium phosphate of pH ranging from 5.3 to 8, in the presence of ATP, adenosine monophosphate, and phenylphosphonic acid. At pH 5.3, submicromolar additions of ATP increase the conductivity of the tBLM incorporating SLN up to a maximum limiting value. The dependence of the conductivity on the ATP concentration satisfies the Michaelis-Menten equation, with an association constant of 0.1 microM. Phenylphosphonium ion and adenosine monophosphate exert an inhibitory effect on membrane permeabilization to phosphate ions by ATP if they are added before ATP, but not if they are added after it. An explanation for this behavior is provided. In conclusion, SLN acts as an ATP-induced phosphate carrier exhibiting a behavior quite similar to that of the unidentified P(i) transporter described previously. No ion-channel activity is exhibited by the T18A mutant of SLN.
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Affiliation(s)
- Lucia Becucci
- Chemistry Department, Florence University, Florence, Italy
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Briand E, Zäch M, Svedhem S, Kasemo B, Petronis S. Combined QCM-D and EIS study of supported lipid bilayer formation and interaction with pore-forming peptides. Analyst 2010; 135:343-50. [DOI: 10.1039/b918288h] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Becucci L, D'Amico M, Daniele S, Olivotto M, Pozzi A, Guidelli R. A metal-supported biomimetic micromembrane allowing the recording of single-channel activity and of impedance spectra of membrane proteins. Bioelectrochemistry 2009; 78:176-80. [PMID: 19726240 DOI: 10.1016/j.bioelechem.2009.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Revised: 08/09/2009] [Accepted: 08/11/2009] [Indexed: 10/20/2022]
Abstract
A novel tethered bilayer lipid micromembrane (tBLmicroM) was prepared and characterized. It consists of a mercury cap electrodeposited on a platinum microelectrode, about 20 microm in diameter. The micromembrane was prepared by tethering to the mercury cap a thiolipid monolayer and by then self-assembling a lipid monolayer on top of it. The thiolipid consisted of a disulfidated tetraoxyethylene hydrophilic spacer covalently linked to two phytanyl chains. Upon incorporating OmpF porin in the tBLmicroM, its single-channel activity was recorded by the patch-clamp technique, and its particular features described. An electrochemical impedance spectrum of the tBLmicroM incorporating OmpF porin is also reported. To the best of our knowledge, this tBLmicroM is the first metal-supported biomimetic micromembrane capable of incorporating non-engineered channel proteins in a functionally active state from their detergent solutions, and of allowing the recording of single-channel activity and of impedance spectra of these proteins via ion translocation into the hydrophilic spacer. The limited spaciousness of the spacer prevents a statistical analysis based on current-amplitude or blockage-time histograms. Nonetheless, the robustness, stability, ease of preparation and disposability of the present tBLmicroM may open the way to the realization of a channel-protein microarray platform allowing a high throughput drug screening.
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Affiliation(s)
- Lucia Becucci
- Department of Chemistry, Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze), Italy.
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On the function of pentameric phospholamban: ion channel or storage form? Biophys J 2009; 96:L60-2. [PMID: 19450461 DOI: 10.1016/j.bpj.2009.03.013] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 02/24/2009] [Accepted: 03/04/2009] [Indexed: 11/22/2022] Open
Abstract
Phospholamban (PLN) is an integral membrane protein that inhibits the sarcoplasmic reticulum Ca(2+)-ATPase, thereby regulating muscle contractility. We report a combined electrochemical and theoretical study demonstrating that the pentameric PLN does not possess channel activity for conducting chloride or calcium ions across the lipid membrane. This suggests that the pentameric configuration of PLN primarily serves as a storage form for the regulatory function of muscle relaxation by the PLN monomer.
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Shi L, Cembran A, Gao J, Veglia G. Tilt and azimuthal angles of a transmembrane peptide: a comparison between molecular dynamics calculations and solid-state NMR data of sarcolipin in lipid membranes. Biophys J 2009; 96:3648-62. [PMID: 19413970 DOI: 10.1016/j.bpj.2009.02.025] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 02/03/2009] [Accepted: 02/12/2009] [Indexed: 02/04/2023] Open
Abstract
We report molecular dynamics simulations in the explicit membrane environment of a small membrane-embedded protein, sarcolipin, which regulates the sarcoplasmic reticulum Ca-ATPase activity in both cardiac and skeletal muscle. In its monomeric form, we found that sarcolipin adopts a helical conformation, with a computed average tilt angle of 28 +/- 6 degrees and azymuthal angles of 66 +/- 22 degrees, in reasonable accord with angles determined experimentally (23 +/- 2 degrees and 50 +/- 4 degrees, respectively) using solid-state NMR with separated-local-field experiments. The effects of time and spatial averaging on both (15)N chemical shift anisotropy and (1)H/(15)N dipolar couplings have been analyzed using short-time averages of fast amide out-of-plane motions and following principal component dynamic trajectories. We found that it is possible to reproduce the regular oscillatory patterns observed for the anisotropic NMR parameters (i.e., PISA wheels) employing average amide vectors. This work highlights the role of molecular dynamics simulations as a tool for the analysis and interpretation of solid-state NMR data.
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Affiliation(s)
- Lei Shi
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota, USA
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Becucci L, Schwan AL, Sheepwash EE, Guidelli R. A new method to evaluate the surface dipole potential of thiol and disulfide self-assembled monolayers and its application to a disulfidated tetraoxyethylene glycol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1828-1835. [PMID: 19170650 DOI: 10.1021/la803282w] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A procedure to evaluate the surface dipole potential chi of thiol and disulfide self-assembled monolayers (SAMs) is described. The procedure consists of self-assembling the monolayers on a hanging mercury drop electrode and of measuring the charge involved in a progressive expansion of the mercury drop. This measurement is then combined with an estimate of the charge density q experienced by diffuse layer ions, obtained by measuring the diffuse layer capacitance of the SAM at different electrolyte concentrations by electrochemical impedance spectroscopy. These chi measurements, combined with chronocoulometric measurements of the total charge density sigma(M) against potential, indicate that SAMs of tetraoxyethylene glycol-D,L-alpha-lipoic acid ester (TEGL), 2,3-di-O-phytanyl-sn-glycerol-1-tetraoxyethylene glycol-D,L-alpha-lipoic ester (DPTL), and trioxyethyleneoxythiol (EO3) on mercury may undergo a reversal in the surface dipole potential of their polyoxyethylene chain with a change in the interfacial electric field. Moreover, TEGL and EO3 form stable SAMs without electron transfer to the metal, while no such conclusion can be drawn for DPTL.
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Affiliation(s)
- Lucia Becucci
- Department of Chemistry, Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy
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27
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Potassium ion transport by gramicidin and valinomycin across a Ag(111)-supported tethered bilayer lipid membrane. Electrochim Acta 2008. [DOI: 10.1016/j.electacta.2008.04.043] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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28
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Faragher RJ, Schwan AL. New Deuterated Oligo(ethylene glycol) Building Blocks and Their Use in the Preparation of Surface Active Lipids Possessing Labeled Hydrophilic Tethers. J Org Chem 2008; 73:1371-8. [DOI: 10.1021/jo701979z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Robert J. Faragher
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Adrian L. Schwan
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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