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Tronin A, Nordgren CE, Strzalka JW, Kuzmenko I, Worcester DL, Lauter V, Freites JA, Tobias DJ, Blasie JK. Direct evidence of conformational changes associated with voltage gating in a voltage sensor protein by time-resolved X-ray/neutron interferometry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:4784-4796. [PMID: 24697545 PMCID: PMC4007984 DOI: 10.1021/la500560w] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Indexed: 06/03/2023]
Abstract
The voltage sensor domain (VSD) of voltage-gated cation (e.g., Na(+), K(+)) channels central to neurological signal transmission can function as a distinct module. When linked to an otherwise voltage-insensitive, ion-selective membrane pore, the VSD imparts voltage sensitivity to the channel. Proteins homologous with the VSD have recently been found to function themselves as voltage-gated proton channels or to impart voltage sensitivity to enzymes. Determining the conformational changes associated with voltage gating in the VSD itself in the absence of a pore domain thereby gains importance. We report the direct measurement of changes in the scattering-length density (SLD) profile of the VSD protein, vectorially oriented within a reconstituted phospholipid bilayer membrane, as a function of the transmembrane electric potential by time-resolved X-ray and neutron interferometry. The changes in the experimental SLD profiles for both polarizing and depolarizing potentials with respect to zero potential were found to extend over the entire length of the isolated VSD's profile structure. The characteristics of the changes observed were in qualitative agreement with molecular dynamics simulations of a related membrane system, suggesting an initial interpretation of these changes in terms of the VSD's atomic-level 3-D structure.
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Affiliation(s)
- Andrey
Y. Tronin
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - C. Erik Nordgren
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Joseph W. Strzalka
- X-ray
Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Ivan Kuzmenko
- X-ray
Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - David L. Worcester
- Department
of Physiology & Biophysics, University
of California Irvine, Irvine, California 92697, United States
| | - Valeria Lauter
- Spallation
Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - J. Alfredo Freites
- Department
of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - Douglas J. Tobias
- Department
of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - J. Kent Blasie
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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Strzalka J, DiMasi E, Kuzmenko I, Gog T, Blasie JK. Resonant x-ray reflectivity from a bromine-labeled fatty acid Langmuir monolayer. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:051603. [PMID: 15600624 DOI: 10.1103/physreve.70.051603] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Revised: 09/07/2004] [Indexed: 05/24/2023]
Abstract
Resonant x-ray reflectivity exploits the energy dependence of atomic scattering factors to locate resonant atoms within the electron density distribution of thin films. We apply the technique to a monolayer of bromo-stearic acid at the air/water interface. The data collection protocol employed cycles through several energies in the vicinity of the bromine K absorption edge and verifies that the energy dependencies observed are indeed resonant effects. The analysis specifies the location of the Br atom with sub-angstrom precision and must consider both the real and imaginary parts of the changes in the scattering factor to be consistent with the known structure and stoichiometry of this test case.
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Affiliation(s)
- Joseph Strzalka
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
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4
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Dalton KA, East JM, Mall S, Oliver S, Starling AP, Lee AG. Interaction of phosphatidic acid and phosphatidylserine with the Ca2+-ATPase of sarcoplasmic reticulum and the mechanism of inhibition. Biochem J 1998; 329 ( Pt 3):637-46. [PMID: 9445393 PMCID: PMC1219087 DOI: 10.1042/bj3290637] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The sarcoplasmic reticulum of skeletal muscle contains anionic phospholipids as well as the zwitterionic phosphatidylcholine and phosphatidylethanolamine. Here we study the effects of anionic phospholipids on the activity of the Ca2+-ATPase purified from the membrane. Reconstitution of the Ca2+-ATPase into dioleoylphosphatidylserine [di(C18:1)PS] or dioleoylphosphatidic acid [di(C18:1)PA] leads to a decrease in ATPase activity. Measurements of the quenching of the tryptophan fluorescence of the ATPase by brominated phospholipids give a relative binding constant for the anionic lipids compared with dioleoylphosphatidylcholine close to 1 and suggest that phosphatidic acid only binds to the ATPase at the bulk lipid sites around the ATPase. Addition of di(C18:1)PS or di(C18:1)PA to the ATPase in the short-chain dimyristoleoylphosphatidylcholine [di(C14:1)PC] reverse the effects of the short-chain lipid on ATPase activity and on Ca2+ binding, as revealed by the response of tryptophan fluorescence intensity to Ca2+ binding. It is concluded that the lipid headgroup and lipid fatty acyl chains have separate effects on the function of the ATPase. The anionic phospholipids have no significant effect on Ca2+ binding to the ATPase; the level of Ca2+ binding to the ATPase, the affinity of binding and the rate of dissociation of Ca2+ are unchanged by reconstitution into di(C18:1)PA. The major effect of the anionic lipids is a reduction in the maximal level of binding of MgATP. This is attributed to the formation of oligomers of the Ca2+-ATPase, in which only one molecule of the ATPase can bind MgATP dimers in di(C18:1)PS and trimers or tetramers in di(C18:1)PA. The rates of phosphorylation and dephosphorylation for the proportion of the ATPase still able to bind ATP are unaffected by reconstitution. Larger changes were observed in the level of phosphorylation of the ATPase by Pi, which became very low in the anionic phospholipids. The fluorescence response to Mg2+ for the ATPase labelled with 4-(bromomethyl)-6,7-dimethoxycoumarin was also changed in di(C18:1)PS and di(C18:1)PA, so that effects of Mg2+ became comparable with those seen on phosphorylation for the unreconstituted ATPase. The anionic phospholipids could induce a conformational change in the ATPase on binding Mg2+ equivalent to that normally induced by phosphorylation or by binding inhibitors such as thapsigargin.
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Affiliation(s)
- K A Dalton
- Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, U.K
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5
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Prokop LA, Stongin RM, Smith AB, Blasie JK, Peticolas LJ, Bean JC. Vectorially oriented monolayers of detergent-solubilized Ca(2+) -ATPase from sarcoplasmic reticulum. Biophys J 1996; 70:2131-43. [PMID: 9172737 PMCID: PMC1225188 DOI: 10.1016/s0006-3495(96)79779-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A method for tethering proteins to solid surfaces has been utilized to form vectorially oriented monolayers of the detergent-solubilized integral membrane protein Ca(2+) -ATPase from the sarcoplasmic reticulum (SR). Bifunctional, organic self-assembled monolayers (SAMs) possessing "headgroup" binding specificity for the substrate and "endgroup" binding specificity for the enzyme were utilized to tether the enzyme to the substrate. Specifically, an amine-terminated 11-siloxyundecaneamine SAM was found to bind the Ca(2+)-ATPase primarily electrostatically. The Ca(2+)-ATPase was labeled with the fluorescent probe 5-(2-[(iodoacetyl)amino]ethyl)aminonaphthalene-1-sulfonic acid before monolayer formation. Consequently, fluorescence measurements performed on amine-terminated SAM/enzyme monolayers formed on quartz substrates served to establish the nature of protein binding. Formation of the monolayers on inorganic multilayer substrates fabricated by molecular beam epitaxy made it possible to use x-ray interferometry to determine the profile structure for the system, which was proved correct by x-ray holography. The profile structures established the vectorial orientation of the Ca(2+)-ATPase within these monolayers, to a spatial resolution of approximately 12 A. Such vectorially oriented monolayers of detergent-solubilized Ca(2+)-ATPase from SR make possible a wide variety of correlative structure/function studies, which would serve to elucidate the mechanism of Ca(2+) transport by this enzyme.
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Affiliation(s)
- L A Prokop
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104, USA.
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6
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Hughes G, Khan YM, East JM, Lee AG. Effects of polycations on Ca2+ binding to the Ca(2+)-ATPase. Biochem J 1995; 308 ( Pt 2):493-9. [PMID: 7772032 PMCID: PMC1136952 DOI: 10.1042/bj3080493] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Spermine and polyarginine have been shown to increase the rate of dissociation of Ca2+ from the Ca(2+)-ATPase of skeletal-muscle sarcoplasmic reticulum. They also decrease the affinity of the ATPase for Mg2+ as detected by changes in the fluorescence intensity of the ATPase labelled with 4-(bromomethyl)-6,7-dimethoxycoumarin (DMC). Polyarginine itself also decreases the fluorescence intensity of DMC-labelled ATPase. These results are consistent with binding of spermine and polyarginine to a gating site controlling the rate of access of Ca2+ to its binding sites on the ATPase. A basic peptide PLN-(1-25) corresponding to residues 1-25 of phospholamban had no effect on the rate of dissociation of Ca2+ or on the fluorescence of DMC-labelled ATPase. Spermine, polyarginine and PLN-(1-25) all increased the equilibrium constant E1/E2, and spermine and polyarginine increased the rate of Ca2+ binding to the ATPase, consistent with an increase in the rate of the E2-->E1 transition. Spermine displaced Tb3+ and Ruthenium Red from the ATPase, consistent with binding in the stalk region of the ATPase. Polyarginine and PLN-(1-25), however, had no effect on Tb3+ or Ruthenium Red binding, suggesting a greater specificity in binding basic peptides to the ATPase than spermine.
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Affiliation(s)
- G Hughes
- Department of Biochemistry, University of Southampton, U.K
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7
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Hao MH, Harvey SC. Active transport of ions across membranes: energetic role of electrostatics and binding site asymmetry. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1234:5-14. [PMID: 7880859 DOI: 10.1016/0005-2736(94)00265-q] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The active transport of ions across a membrane by an ATP-driven electrogenic ion pump is often described by an 'alternate access' model. The position of the binding site is assumed to be unchanged as the binding cavity opens alternatively to the uptake and discharge sides of the membrane. The ion binding affinity is higher on the uptake side of the membrane than on the discharge side. This difference in affinities is related to the maximum transport rate and to the efficiency with which ATP hydrolysis is coupled to active transport. Here we examine the electrostatic contribution to binding affinities, using a simple geometry for a model membrane-protein system, a continuum dielectric approximation, and a numerical method to calculate binding energy as a function of the binding site location. If the binding site is located asymmetrically, being further from the uptake side of the membrane than from the discharge side, there is a significant difference in binding free energy between the uptake and discharge states. This asymmetry can produce differences in affinities that are consistent with those measured for biological active transport systems. These results may account for the observed asymmetric location of the calcium binding site in the calcium ATPases from sarcoplasmic reticulum and from the plasma membrane. Electrostatic energy differences associated with binding site asymmetry may be a general feature of electrogenic transmembrane ion pumps.
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Affiliation(s)
- M H Hao
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham 35294-0005
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8
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Abstract
The Ca-ATPase in the cardiac sarcoplasmic reticulum membrane is regulated by an amphipathic transmembrane protein, phospholamban. We have used time-resolved phosphorescence anisotropy to detect the microsecond rotational dynamics, and thereby the self-association, of the Ca-ATPase as a function of phospholamban phosphorylation and physiologically relevant calcium levels. The phosphorylation of phospholamban increases the rotational mobility of the Ca-ATPase in the sarcoplasmic reticulum bilayer, due to a decrease in large-scale protein association, with a [Ca2+] dependence parallel to that of enzyme activation. These results support a model in which phospholamban phosphorylation or calcium free the enzyme from a kinetically unfavorable associated state.
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Affiliation(s)
- J Voss
- Department of Biochemistry, University of Minnesota Medical School, Minneapolis 55455
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9
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Asturias FJ, Fischetti RF, Blasie JK. Changes in the relative occupancy of metal-binding sites in the profile structure of the sarcoplasmic reticulum membrane induced by phosphorylation of the Ca2+ATPase enzyme in the presence of terbium: a time-resolved, resonance x-ray diffraction study. Biophys J 1994; 66:1665-77. [PMID: 8061215 PMCID: PMC1275886 DOI: 10.1016/s0006-3495(94)80958-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Time-resolved, terbium resonance x-ray diffraction experiments have provided the locations of three different high-affinity metal-binding/transport sites on the Ca2+ATPase enzyme in the profile structure of the sarcoplasmic reticulum (SR) membrane. By considering these results in conjunction with the known, moderate-resolution profile structure of the SR membrane (derived from nonresonance x-ray and neutron diffraction studies), it was determined that the three metal-binding sites are located at the "headpiece/stalk" junction in the Ca2+ATPase profile structure, in the "transbilayer" portion of the enzyme profile near the center of the membrane phospholipid bilayer, and at the intravesicular surface of the membrane profile. All three metal-binding sites so identified are simultaneously occupied in the unphosphorylated enzyme conformation. Phosphorylation of the ATPase causes a redistribution of metal density among the sites, resulting in a net movement of metal density toward the intravesicular side of the membrane, i.e., in the direction of calcium active transport. We propose that this redistribution of metal density is caused by changes in the relative binding affinities of the three sites, mediated by local structural changes at the sites resulting from the large-scale (i.e., long-range) changes in the profile structure of the Ca2+ATPase induced by phosphorylation, as reported in an accompanying paper. The implications of these results for the mechanism of calcium active transport by the SR Ca2+ATPase are discussed briefly.
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Affiliation(s)
- F J Asturias
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104
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10
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Asturias FJ, Fischetti RF, Blasie JK. Changes in the profile structure of the sarcoplasmic reticulum membrane induced by phosphorylation of the Ca2+ ATPase enzyme in the presence of terbium: a time-resolved x-ray diffraction study. Biophys J 1994; 66:1653-64. [PMID: 8061214 PMCID: PMC1275885 DOI: 10.1016/s0006-3495(94)80957-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The design of the time-resolved x-ray diffraction experiments reported in this and an accompanying paper was based on direct measurements of enzyme phosphorylation using [gamma-32P]ATP that were employed to determine the extent to which the lanthanides La3+ and Tb3+ activate phosphorylation of the Ca2+ATPase and their effect on the kinetics of phosphoenzyme formation and decay. We found that, under the conditions of our experiments, the two lanthanides are capable of activating phosphorylation of the ATPase, resulting in substantial levels of phosphoenzyme formation and they slow the formation and dramatically extend the lifetime of the phosphorylated enzyme conformation, as compared with calcium activation. The results from the time-resolved, nonresonance x-ray diffraction work reported in this paper are consistent with the enzyme phosphorylation experiments; they indicate that the changes in the profile structure of the SR membrane induced by terbium-activated phosphorylation of the ATPase enzyme are persistent over the much longer lifetime of the phosphorylated enzyme and are qualitatively similar to the changes induced by calcium-activated phosphorylation, but smaller in magnitude. These results made possible the time-resolved, resonance x-ray diffraction studies reported in an accompanying paper utilizing the resonance x-ray scattering from terbium, replacing calcium, to determine not only the location of high-affinity metal-binding sites in the SR membrane profile, but also the redistribution of metal density among those sites upon phosphorylation of the Ca2+ATPase protein, as facilitated by the greatly extended lifetime of the phosphoenzyme.
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Affiliation(s)
- F J Asturias
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104
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11
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Corbalan-Garcia S, Teruel JA, Gomez-Fernandez JC. Intramolecular distances within the Ca(2+)-ATPase from sarcoplasmic reticulum as estimated through fluorescence energy transfer between probes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 217:737-44. [PMID: 8223616 DOI: 10.1111/j.1432-1033.1993.tb18300.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Fluorescence energy transfer measurements have been carried out to estimate intramolecular distances between probes bound to Ca(2+)-transporting ATPase (Ca(2+)-ATPase) as well as distances between these probes and the phospholipid headgroup. The nucleotide binding site was monitored by using 1,N6-ethenoadenosine 5'-triphosphate, a fluorescent analogue of ATP, and also by labelling Lys515 with fluorescein 5'-isothiocyanate. Three different cysteine residues were individually labelled using the following probes: 5-[(2-iodoacetyl)aminoethyl]amino-naphthalene-1-sulfonic acid (I-AEDANS), 7-chloro-4-nitro-2,1,3-benzoxadiazole (NBD-Cl) and fluorescent maleimides. The surface of the membrane was labelled by reconstitution with fluorescent phospholipids (fluorescein and rhodamine derivatives). We found a distance of 4.1 nm from the nucleotide binding site to NBD (at Cys344), and the same distance to fluorescent maleimides (at Cys364). The AEDANS label (at Cys670,672) was found separated 3.5 nm from NBD, 4.4 nm from fluorescent maleimides, and 3.9 nm from the lipid matrix. The NBD label was 3.2 nm apart from fluorescent maleimides and 2.2 nm from the lipid matrix. Finally, fluorescent maleimides were found to be located 4.2 nm above the membrane surface. All these distances agree with a molecular model in which NBD is located in the stalk portion of the Ca(2+)-ATPase, near the surface of the membrane, and the rest of the probes are above it, in the globular domain of the protein.
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Affiliation(s)
- S Corbalan-Garcia
- Departamento de Bioquímica y Biología Molecular A, Edificio de Veterinaria, Universidad de Murcia, Spain
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12
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Membrane topology of a P-type ATPase. The MgtB magnesium transport protein of Salmonella typhimurium. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)41553-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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13
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Andersen JP, Vilsen B. Functional consequences of substitution of the seven-residue segment LysIleArgAspGlnMetAla240 located in the stalk helix S3 of the Ca(2+)-ATPase of sarcoplasmic reticulum. Biochemistry 1993; 32:10015-20. [PMID: 8399128 DOI: 10.1021/bi00089a017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Site-directed mutagenesis was used to substitute the seven-residue segment LysIleArgAspGlnMetAla240 located at the NH2- terminal end of the "stalk" helix S3, near the beta-strand domain, in the sarcoplasmic reticulum Ca(2+)-ATPase of rabbit fast twitch muscle, with the corresponding Na+,K(+)-ATPase segment ArgIleAlaThrLeuAlaSer. This led to a new phenotypic variant of Ca(2+)-ATPase. The overall turnover rates for Ca2+ transport and ATP hydrolysis measured at 27 and 37 degrees C, respectively, were reduced to 30-40% of the wild-type rates. Analysis of the phosphoenzyme intermediates at 0 degrees C showed that the ADP-insensitive phosphoenzyme intermediate accumulated under conditions where the ADP-sensitive phosphoenzyme intermediate predominated in the wild-type Ca(2+)-ATPase. The rate of dephosphorylation of the ADP-insensitive phosphoenzyme intermediate formed through the forward reaction with ATP, or in the "backdoor" reaction with Pi, was reduced severalfold in the mutant relative to the dephosphorylation rate measured in the wild type, but there was no significant difference between the mutant and the wild type with respect to the apparent affinity for Pi measured under equilibrium conditions. The mutant was much less susceptible to inhibition by vanadate than the wild type, under equilibrium conditions as well as during turnover with ATP and Ca2+. These observations suggest that the transition state in the hydrolysis of the aspartyl phosphate bond in the ADP-insensitive phosphoenzyme intermediate was destabilized in the mutant.
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Affiliation(s)
- J P Andersen
- Danish Biomembrane Research Centre, University of Aarhus
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14
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DeLong LJ, Blasie JK. Effect of Ca2+ binding on the profile structure of the sarcoplasmic reticulum membrane using time-resolved x-ray diffraction. Biophys J 1993; 64:1750-9. [PMID: 8369405 PMCID: PMC1262509 DOI: 10.1016/s0006-3495(93)81546-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
A number of studies have indicated that Ca(2+)-ATPase, the integral membrane protein of the sarcoplasmic reticulum (SR) membrane, undergoes some structural change upon Ca2+ binding to its high affinity binding sites (i.e., upon conversion of the E1 to the CaxE1 form of the enzyme). We have used x-ray diffraction to study the changes in the electron density profile of the SR membrane upon high-affinity Ca2+ binding to the enzyme in the absence of enzyme phosphorylation. The photolabile Ca2+ chelator DM-nitrophen was used to rapidly release Ca2+ into the extravesicular spaces throughout an oriented SR membrane multilayer and thereby synchronously in the vicinity of the high affinity binding sites of each enzyme molecule in the multilayer. A critical control was developed to exclude possible artifacts arising from heating and non-Ca2+ photolysis products in the membrane multilayer specimens upon photolysis of the DM-nitrophen. Upon photolysis, changes in the membrane electron density profile arising from high-affinity Ca2+ binding to the enzyme are found to be localized to three different regions within the profile. These changes can be attributed to the added electron density of the Ca2+ bound at three discrete sites centered at 5, approximately 30, and approximately 67 A in the membrane profile, but they also require decreased electron density within the cylindrically averaged profile structure of the Ca(2+)-ATPase immediately adjacent (< 15 A) to these sites. The locations of these three Ca2+ binding sites in the SR membrane profile span most of the membrane profile in the absence of enzyme phosphorylation,in agreement with the locations of lanthanide (Tb3+ and La3+) binding sites in the membrane profile determined independently by using resonance x-ray diffraction.
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Affiliation(s)
- L J DeLong
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104
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15
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Kalabokis VN, Hardwicke PM. Effect of the biochemical state of the Ca-ATPase protein of scallop sarcoplasmic reticulum on its interaction with trans-parinaric acid. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1147:35-41. [PMID: 8466929 DOI: 10.1016/0005-2736(93)90313-o] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The polyene fluorescent probe trans-parinaric acid (tPA) was used to compare lipid-protein interactions in the scallop fragmented sarcoplasmic reticulum (FSR) between biochemical states where the Ca-ATPase molecules were arranged differently in the membrane and had different tertiary conformations. The state of the bulk lipid phase was examined over the temperature range -3 to +32 degrees C by exciting the tPA directly at 320 nm. The state of the system close to the Ca-ATPase protein was followed over the same temperature range by indirectly exciting the tPA through resonance energy transfer from the Ca-ATPase protein, with approximately one twenty-fifth the quantum yield of the directly excited probe. Raising the tPA/lipid ratio in the membrane to high levels (approx. 1:9), caused the quantum yield of indirectly excited tPA to reach a maximum, which may reflect saturation of the annular lipid phase with the probe, or contribution to the fluorescence from indirectly excited tPA bound directly to the protein. In the presence of 0.1 M KCl, a thermal perturbation was observed at approx. 7 degrees C using indirect excitation when the Ca(2+)-binding sites on the Ca-ATPase were occupied, and the subunits were disorganized. This transition was not detected in the presence of 0.1 M KCl and EGTA, when the Ca(2+)-binding sites were empty, and the Ca-ATPase subunits were organized in dimeric arrays. The transition seen with the E1(Ca2+)2 form of the membrane may involve an event at the protein/lipid interface, or a change in the environment of tPA bound to the Ca-ATPase. The temperature at which the perturbation occurs is close to that of a discontinuity in the Arrhenius plot of the Ca-ATPase enzyme activity determined in the presence of 0.1 M KCl (Kalabokis, V.N. and Hardwicke, P.M.D. (1988) J. Biol. Chem. 263, 15184-15188). No perturbation was observed in the bulk properties of the lipid component of the membrane in either the E1(Ca2+)2 or E2 states.
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Affiliation(s)
- V N Kalabokis
- Department of Medical Biochemistry, Southern Illinois University, Carbondale
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16
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Mata AM, Stefanova HI, Gore MG, Khan YM, East JM, Lee AG. Localization of Cys-344 on the (Ca(2+)-Mg(2+)-ATPase of sarcoplasmic reticulum using resonance energy transfer. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1147:6-12. [PMID: 8466933 DOI: 10.1016/0005-2736(93)90309-n] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
4-Bromomethyl-6,7-dimethoxy-coumarin labels the (Ca(2+)-Mg(2+)-ATPase of skeletal muscle sarcoplasmic reticulum at Cys-344. Resonance energy transfer has been used to measure the distance between this site and Lys-515 labelled with fluorescein isothiocyanate as about 37 A. The height of Cys-344 above the phospholipid/water interface has been measured by resonance energy transfer for the ATPase reconstituted into bilayers containing fluorescein-labelled phosphatidylethanolamine; the height was found to be about 45 A. None of these distances was found to alter on changing pH, or on addition of Mg2+, Ca2+ or vanadate. Quenching of the fluorescence of the coumarin-labelled ATPase with KI suggested that the fluorophore is not fully exposed on the ATPase.
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Affiliation(s)
- A M Mata
- SERC Centre for Molecular Recognition, University of Southampton, UK
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17
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Bigelow DJ, Inesi G. Contributions of chemical derivatization and spectroscopic studies to the characterization of the Ca2+ transport ATPase of sarcoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1113:323-38. [PMID: 1450205 DOI: 10.1016/0304-4157(92)90005-u] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- D J Bigelow
- Department of Biochemistry, University of Kansas, Lawrence
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18
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Blasie JK, Asturias FJ, DeLong LJ. Time-resolved X-ray diffraction studies on the mechanism of active Ca2+ transport by the sarcoplasmic reticulum Ca2+ ATPase. Ann N Y Acad Sci 1992; 671:11-8. [PMID: 1288319 DOI: 10.1111/j.1749-6632.1992.tb43780.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- J K Blasie
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104
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Mata AM, Matthews I, Tunwell RE, Sharma RP, Lee AG, East JM. Definition of surface-exposed and trans-membranous regions of the (Ca(2+)-Mg2+)-ATPase of sarcoplasmic reticulum using anti-peptide antibodies. Biochem J 1992; 286 ( Pt 2):567-80. [PMID: 1388354 PMCID: PMC1132935 DOI: 10.1042/bj2860567] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Peptides have been synthesized representing parts of the transduction, phosphorylation, nucleotide-binding and hinge domains of the (Ca(2+)-Mg2+)-ATPase of skeletal muscle sarcoplasmic reticulum (SR), and corresponding to segments of all of the postulated short inter-membranous loops of the (Ca(2+)-Mg2+)-ATPase (residues 77-88, 277-287, 780-791, 808-818, 915-924 and 949-958). A number of antibodies raised to these peptides have been shown to bind to the ATPase, defining surface-exposed regions. Many of these are concentrated in the phosphorylation and nucleotide-binding domains, suggesting that these domains could be exposed on the top surface of the ATPase. The cytoplasmic location of the loop containing residues 808-818 was confirmed by the finding that proteinase K treatment of intact SR vesicles enhanced the binding of antibodies against this segment. These findings support the 10-alpha-helix model of the ATPase. These results also suggest that only inter-membranous loops larger than about 20 residues are likely to be detected by immunological methods in transmembranous proteins. Binding of anti-peptide antibodies to proteolytic fragments of the ATPase has been used to define the domain structure of the enzyme. Some of the anti-peptide antibodies have been characterized by studying their binding to sets of hexameric peptides synthesized on plastic pegs. A wide pattern of responses is observed, with a restricted range of epitopes being recognized by each anti-peptide antibody.
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Affiliation(s)
- A M Mata
- Department of Biochemistry, University of Southampton, U.K
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20
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Abstract
The gram-negative bacterium Salmonella typhimurium possesses three distinct Mg2+ transport systems, encoded by the corA, mgtA, and mgtB loci. The CorA transport system is the constitutive Mg2+ influx system. It can also mediate Mg2+ efflux at very high extracellular Mg2+ concentrations. In contrast, the MgtA and MgtB Mg2+ transport systems are normally expressed only at low extracellular Mg2+ concentrations. A strain of S. typhimurium was constructed by mutagenesis which lacks Mg2+ transport and requires 100 mM Mg2+ for growth. Using this strain, both the MgtA and MgtB transport systems were cloned by complementation of the strains inability to grow without Mg2+ supplementation. After sequencing and further genetic analysis, the MgtB system appears to be an operon composed of the mgtC and mgtB genes (5' to 3'). The downstream mgtB gene encodes the 102 kDa MgtB protein which by sequence analysis is clearly a P-type ATPase. Interestingly, while MgtB has relatively poor homology to other known prokaryotic P-type ATPases, it is highly homologous to mammalian reticular Ca(2+)-ATPases. MgtC is a 22.5 kDa hydrophobic membrane protein that lacks homology to any known protein. Transposon insertions in this gene abolish uptake by the MgtB transport system. We hypothesize that MgtC is a subunit of the MgtB ATPase involved either in proper insertion of MgtB into the membrane or possibly in binding of extracellular Mg2+ for delivery to the ATPase subunit. The sequence of the MgtA gene has recently been completed, and it too is a P-type ATPase more similar to eukaryotic than prokaryotic P-type ATPases. Expression of both MgtA and MgtB are highly regulated by the concentration of extracellular Mg2+. Transcription of mgtB can be increased about 1000 fold by lowering Mg2+ from 1 mM to 1 microM. Likewise, when mgtB is expressed from a multicopy plasmid, a similar decrease in extracellular Mg2+ greatly increases transport. Under growth conditions of limiting Mg2+, MgtB becomes the dominant Mg2+ influx system in S. typhimurium. Even so, since MgtB (and MgtA) mediate only influx of Mg2+, it is unclear why the cell requires energy from ATP to mediate Mg2+ entry into the cell down a large electrochemical gradient. Further studies of the structure-function and energetics of these novel Mg2+ influx P-type ATPases should yield insights into the function of P-type ATPases in general as well as information about the regulation of cellular Mg2+ fluxes.
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Affiliation(s)
- M E Maguire
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965
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21
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Henao F, Orlowski S, Merah Z, Champeil P. The metal sites on sarcoplasmic reticulum membranes that bind lanthanide ions with the highest affinity are not the ATPase Ca2+ transport sites. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50018-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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22
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Clarke DL, Collins MA. Simulation of coherent energy transfer in an alpha-helical peptide by Fermi resonance. Biophys J 1992; 61:316-33. [PMID: 1547322 PMCID: PMC1260249 DOI: 10.1016/s0006-3495(92)81839-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A mechanism by which NH stretching quanta are coherently transported along a chain of hydrogen bonded peptide groups is demonstrated by classical simulation of a section of the alpha-helical peptide poly(L-alanine). Vibrational motion takes place on a complex energy surface constructed from earlier ab initio and empirical surfaces. A speculative hypothesis of the biological role of this mechanism is presented, and the critical parameters governing the dynamics are identified and discussed.
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Affiliation(s)
- D L Clarke
- Research School of Chemistry, Australian National University, Canberra, A.C.T
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23
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Chapter 4 The Neurospora crassa plasma membrane H+ -ATPase. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/s0167-7306(08)60066-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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P-type ion pumps: structure determination may soon catch up with structure predictions. Curr Opin Struct Biol 1991. [DOI: 10.1016/s0959-440x(05)80077-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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