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González DA, Ostuni MA, Lacapère JJ, Alonso GL. Stoichiometry of ATP and metal cofactor interaction with the sarcoplasmic reticulum Ca(2+)-ATPase: a binding model accounting for radioisotopic and fluorescence results. Biophys Chem 2006; 124:27-34. [PMID: 16784803 DOI: 10.1016/j.bpc.2006.05.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Accepted: 05/21/2006] [Indexed: 11/15/2022]
Abstract
Sarcoplasmic reticulum Ca-ATPase belongs to the P-type ATPases family and transports calcium at the expense of ATP hydrolysis. For years, a complex pattern of activity has been observed as a function of ATP and metal cofactor concentrations, leaving the stoichiometry of both metal and ATP in the active site as an open question. In agreement with recent structural studies we present here-using Mn as analogue of Mg-radioisotopic and fluorescence results showing that two metal ions bind to the Ca-ATPase favoring ATP binding. We further show that low ATP concentration favors the binding of these ions, whereas high ATP concentration is inhibitory. We propose a binding model for ATP and metal ions, which permits simulation of our data. Finally, we suggest that (i) the contribution of two metal ions as cofactors of ATP is essential to get maximal activity; (ii) the contribution of two ATP molecules can activate or inhibit the Ca-ATPase depending on metal concentration.
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Affiliation(s)
- Débora A González
- Cátedra de Biofísica, Facultad de Odontología, Universidad de Buenos Aires, M.T. De Alvear 2142 (C1122AAH) Buenos Aires, Argentina.
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2
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Stokes DL, Green NM. Structure and function of the calcium pump. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2003; 32:445-68. [PMID: 12598367 DOI: 10.1146/annurev.biophys.32.110601.142433] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Active transport of cations is achieved by a large family of ATP-dependent ion pumps, known as P-type ATPases. Various members of this family have been targets of structural and functional investigations for over four decades. Recently, atomic structures have been determined for Ca2+-ATPase by X-ray crystallography, which not only reveal the architecture of these molecules but also offer the opportunity to understand the structural mechanisms by which the energy of ATP is coupled to calcium transport across the membrane. This energy coupling is accomplished by large-scale conformational changes. The transmembrane domain undergoes plastic deformations under the influence of calcium binding at the transport site. Cytoplasmic domains undergo dramatic rigid-body movements that deliver substrates to the catalytic site and that establish new domain interfaces. By comparing various structures and correlating functional data, we can now begin to associate the chemical changes constituting the reaction cycle with structural changes in these domains.
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Affiliation(s)
- David L Stokes
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, New York University School of Medicine, New York, New York 10012, USA.
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Ma H, Inesi G, Toyoshima C. Substrate-induced conformational fit and headpiece closure in the Ca2+ATPase (SERCA). J Biol Chem 2003; 278:28938-43. [PMID: 12750373 DOI: 10.1074/jbc.m304120200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protection of the Ca2+ATPase (SERCA) from proteinase K digestion has been observed following the addition of Ca2+, Mg2+, and nucleotide and interpreted as a substrate-dependent conformational change (1). The protected digestion site is located on the loop connecting the A domain and the M3 transmembrane helix. We studied by mutational analysis the protective effect of AMP-PCP, an ATP analog that is not utilized for enzyme phosphorylation. We found that the nucleotide protective effect is interfered with by single mutations of Arg-560 and Glu-439 in the N domain and Lys-352, Lys-684, Thr-353, Asp-703, and Asp-707 in the P domain. This is consistent with a transition from the open to the compact configuration of the ATPase headpiece and approximation of the N and P domains by interactions with the nucleotide adenosine and phosphate moieties, respectively. The A domain-M3 loop is consequently involved. Protection by nucleotide substrate increased following the mutations of Asp-351 (the residue undergoing phosphorylation by ATP) and neighboring Asn-706 to Ala, underlying the importance of side chain specificity in positioning the nucleotide terminal phosphate and limiting the stability of the substrate-enzyme complex. Protection is not observed when AMP-PCP is added in the absence of Ca2+ or following mutations (E771Q or N796A) that interfere with Ca2+ binding. Therefore, nucleotide binds to the Ca2+-activated enzyme in the open headpiece conformation and the consequent approximation of the N and P domains occurs while the transmembrane domain is still in the Ca2+-bound conformation. Mg2+ is not required for the protective effect of nucleotide, even though it is specifically required for the subsequent catalytic reactions.
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Affiliation(s)
- Hailun Ma
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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Abstract
The report of the crystal structure of the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum in its Ca(2+)-bound form [Toyoshima, Nakasako and Ogawa (2000) Nature (London) 405, 647-655] provides an opportunity to interpret much kinetic and mutagenic data on the ATPase in structural terms. There are no large channels leading from the cytoplasmic surface to the pair of high-affinity Ca(2+) binding sites within the transmembrane region. One possible access pathway involves the charged residues in transmembrane alpha-helix M1, with a Ca(2+) ion passing through the first site to reach the second site. The Ca(2+)-ATPase also contains a pair of binding sites for Ca(2+) that are exposed to the lumen. In the four-site model for transport, phosphorylation of the ATPase leads to transfer of the two bound Ca(2+) ions from the cytoplasmic to the lumenal pair of sites. In the alternating four-site model for transport, phosphorylation leads to release of the bound Ca(2+) ions directly from the cytoplasmic pair of sites, linked to closure of the pair of lumenal binding sites. The lumenal pair of sites could involve a cluster of conserved acidic residues in the loop between M1 and M2. Since there is no obvious pathway from the high-affinity sites to the lumenal surface of the membrane, transport of Ca(2+) ions must involve a significant change in the packing of the transmembrane alpha-helices. The link between the phosphorylation domain and the pair of high-affinity Ca(2+) binding sites is probably provided by two small helices, P1 and P2, in the phosphorylation domain, which contact the loop between transmembrane alpha-helices M6 and M7.
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Affiliation(s)
- A G Lee
- Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK.
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Stokes DL, Green NM. Modeling a dehalogenase fold into the 8-A density map for Ca(2+)-ATPase defines a new domain structure. Biophys J 2000; 78:1765-76. [PMID: 10733958 PMCID: PMC1300772 DOI: 10.1016/s0006-3495(00)76727-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Members of the large family of P-type pumps use active transport to maintain gradients of a wide variety of cations across cellular membranes. Recent structures of two P-type pumps at 8-A resolution have revealed the arrangement of transmembrane helices but were insufficient to reveal the architecture of the cytoplasmic domains. However, recent proposals of a structural homology with a superfamily of hydrolases offer a new basis for modeling these domains. In the current work, we have extended the sequence comparison for the superfamily and delineated domains in the 8-A density map of Ca(2+)-ATPase. The homology suggests a new domain structure for Ca(2+)-ATPase and, specifically, that the phosphorylation domain adopts a Rossman fold. Accordingly, the atomic structure of L-2 haloacid dehalogenase has been fitted into the relevant domain of Ca(2+)-ATPase. The resulting model suggests the existence of two ATP sites at the interface between two domains. Based on this new model, we are able to reconcile numerous results of mutagenesis and chemical cross-linking within the catalytic domains. Furthermore, we have used the model to predict the configuration of Mg.ATP at its binding site. Based on this prediction, we propose a mechanism, involving a change in Mg(2+) liganding, for initiating the domain movements that couple sites of ion transport to ATP hydrolysis.
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Affiliation(s)
- D L Stokes
- Skirball Institute of Biomolecular Research, Department of Cell Biology, New York University School of Medicine, New York, New York 10016, USA.
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McIntosh DB, Woolley DG, MacLennan DH, Vilsen B, Andersen JP. Interaction of nucleotides with Asp(351) and the conserved phosphorylation loop of sarcoplasmic reticulum Ca(2+)-ATPase. J Biol Chem 1999; 274:25227-36. [PMID: 10464243 DOI: 10.1074/jbc.274.36.25227] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The nucleotide binding properties of mutants with alterations to Asp(351) and four of the other residues in the conserved phosphorylation loop, (351)DKTGTLT(357), of sarcoplasmic reticulum Ca(2+)-ATPase were investigated using an assay based on the 2', 3'-O-(2,4,6-trinitrophenyl)-8-azidoadenosine triphosphate (TNP-8N(3)-ATP) photolabeling of Lys(492) and competition with ATP. In selected cases where the competition assay showed extremely high affinity, ATP binding was also measured by a direct filtration assay. At pH 8.5 in the absence of Ca(2+), mutations removing the negative charge of Asp(351) (D351N, D351A, and D351T) produced pumps that bound MgTNP-8N(3)-ATP and MgATP with affinities 20-156-fold higher than wild type (K(D) as low as 0.006 microM), whereas the affinity of mutant D351E was comparable with wild type. Mutations K352R, K352Q, T355A, and T357A lowered the affinity for MgATP and MgTNP-8N(3)-ATP 2-1000- and 1-6-fold, respectively, and mutation L356T completely prevented photolabeling of Lys(492). In the absence of Ca(2+), mutants D351N and D351A exhibited the highest nucleotide affinities in the presence of Mg(2+) and at alkaline pH (E1 state). The affinity of mutant D351A for MgATP was extraordinarily high in the presence of Ca(2+) (K(D) = 0.001 microM), suggesting a transition state like configuration at the active site under these conditions. The mutants with reduced ATP affinity, as well as mutants D351N and D351A, exhibited reduced or zero CrATP-induced Ca(2+) occlusion due to defective CrATP binding.
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Affiliation(s)
- D B McIntosh
- Department of Chemical Pathology, University of Cape Town Medical School, 7925 Cape Town, South Africa.
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Mintz E, Guillain F. Ca2+ transport by the sarcoplasmic reticulum ATPase. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1318:52-70. [PMID: 9030255 DOI: 10.1016/s0005-2728(96)00132-6] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- E Mintz
- Centre National de la Recherche Scientifique, Département de Biologie Cellulaire et Moléculaire, Centre d'Etudes de Saclay, Gif-sur-Yvette, France
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The ATP Binding Sites of P-Type ION Transport ATPases: Properties, Structure, Conformations, and Mechanism of Energy Coupling. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1569-2558(08)60152-6] [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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Takara D, Alonso GL. Effect of haloperidol on the sarcoplasmic reticulum Ca-dependent adenosine triphosphatase. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1314:57-65. [PMID: 8972718 DOI: 10.1016/s0167-4889(96)00076-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Several effects of the neuroleptic agent haloperidol on the sarcoplasmic reticulum (SR) Ca-dependent adenosine triphosphatase (Ca-ATPase) and Ca transport are described. Haloperidol inhibits the Ca-ATPase activity in the presence of calcimycin. The effect depends on the conditions of preexposure of the membranes to the drug: the inhibition increases with the preincubation time; Ca and Mg protect the enzyme against the effect of the drug. The inhibitory effect of haloperidol decreases upon increasing [Ca2+], at constant [Mg], and disappears at 20 mM [Mg] for any [Ca2+], and at 0.5 mM [Ca2+] for any [Mg2+]. Haloperidol also inhibits phosphorylation of the enzyme by Pi, and ATP-dependent Ca2+ uptake, in both cases with apparent Ki = 0.10-0.15 mM, and increases the rate of Ca efflux from preloaded vesicles in this concentration range. The results suggest that haloperidol interacts with the catalytic site, interfering with the effect of the divalent catalytic cation, but not at other steps of the enzymatic cycle, where Mg2+ and Ca2+ are also activators. They are consistent with a reaction model where haloperidol interacts with the E2 conformers of the enzyme, with lower affinity for the phosphoenzyme than for the dephospho species. The inhibition of Ca uptake by SR vesicles is ascribed to an increased Ca2+ permeability rather than to the inhibition of the Ca-ATPase, which requires higher concentrations of the drug.
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Affiliation(s)
- D Takara
- Cátedra de Biofísica, Facultad de Odontología, Universidad de Buenos Aires, Argentina
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González DA, Alonso GL, Lacapère JJ. Manganese as a cosubstrate for the phosphorylation of the sarcoplasmic reticulum Ca-dependent adenosine triphosphatase with orthophosphate. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1276:188-94. [PMID: 8856104 DOI: 10.1016/0005-2728(96)00076-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The phosphorylation of the sarcoplasmic reticulum Ca-ATPase (EC 3.6.1.38) with P(i) was characterized using Mn as a Mg analogue. Steady state and transient fluorescence and radioisotopic techniques were used; the affinities of Mn and P(i) for the enzyme and the rate constants of the phosphorylation and dephosphorylation reactions were determined, under several conditions. The reactions were carried out at pH 5.5 to minimize the binding of contaminant Ca to the transport sites, thus avoiding the use of Ca chelators. The apparent affinity of Mn binding at low [Mn] is larger in the absence of P(i) (35 microM) than in the presence of saturating P(i) (70 microM). On the contrary, the apparent affinity of Mn for the formation of the phosphoenzyme increases, from 1.5 mM to 0.15 mM, upon increasing [P(i)] in the millimolar range. The apparent affinty of P(i) for the formation of the phosphoenzyme also increases, from 2.2 mM to 0.2 mM, upon increasing [Mn] in the millimolar range. The equilibrium of the phosphoenzyme with the noncovalent Mn.P(i). Enzyme complex favors the covalent species. The simulation of a reaction model including the random binding of 2 Mn and I P(i) per mol of ATPase and a noncovalent complex in equilibrium with the phosphoenzyme, using a set of equilibrium constants deduced from the results, agree with the experimental data.
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Affiliation(s)
- D A González
- Cátedra de Biofísica, Facultad de Odontología, Universidad de Buenos Aires, Argentina.
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Mintz E, Guillain F. How do Ca2+ ions pass through the sarcoplasmic reticulum membrane. Biosci Rep 1995; 15:377-85. [PMID: 8825039 DOI: 10.1007/bf01788369] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We propose an overview of the mechanism of Ca2+ transport through the sarcoplasmic reticulum membrane via the Ca(2+)-ATPase. We describe cytoplasmic calcium binding, calcium occlusion in the membrane and lumenal calcium dissociation. A channel-like structure is discussed and related to structural data on the membranous domain of the Ca(2+)-ATPase.
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Affiliation(s)
- E Mintz
- Unité de Recherche 1290 Associée au Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
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Coan C, Jakobs P, Ji JY, Murphy AJ. Sarcoplasmic reticulum calcium ATPase. Labeling of a putative Mg2+ site by reaction with a carbodiimide and a spin-label. FEBS Lett 1993; 335:33-6. [PMID: 7902300 DOI: 10.1016/0014-5793(93)80433-u] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The sarcoplasmic reticulum Ca(2+)-ATPase loses hydrolytic activity and the ability to be phosphorylated by Pi following incubation with EDC [1-ethyl-3-(3-dimethylaminopropyl)carbodiimide]. 4 nmol of tempamine per mg SR protein can be coupled to either a glu or an asp side chain through the EDC reaction. Mg2+ protects against loss of activity and tempamine labeling with a mid-point of about 3 mM in the absence of Ca2+. This is similar to the Kd for a Mg2+ that serves as a cofactor in enzyme phosphorylation. The Mg2+ protection constant is lowered by an order of magnitude when Ca2+ is bound to the transport sites. It is suggested that control of the Mg2+ binding site affinity may be part of the mechanism of enzyme activation by Ca2+.
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Affiliation(s)
- C Coan
- Department of Physiology, School of Dentistry, University of the Pacific, San Francisco, CA 94115
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