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Nakamura J, Maruyama Y, Tajima G, Hayakawa S, Suwa M, Sato C. Ca 2+ Dependent Formation/Collapse of Cylindrical Ca 2+-ATPase Crystals in Scallop Sarcoplasmic Reticulum (SR) Vesicles: A Possible Dynamic Role of SR in Regulation of Muscle Contraction. Int J Mol Sci 2023; 24:ijms24087080. [PMID: 37108240 PMCID: PMC10139091 DOI: 10.3390/ijms24087080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 03/28/2023] [Accepted: 03/29/2023] [Indexed: 04/29/2023] Open
Abstract
[Ca2+]-dependent crystallization of the Ca2+-ATPase molecules in sarcoplasmic reticulum (SR) vesicles isolated from scallop striated muscle elongated the vesicles in the absence of ATP, and ATP stabilized the crystals. Here, to determine the [Ca2+]-dependence of vesicle elongation in the presence of ATP, SR vesicles in various [Ca2+] environments were imaged using negative stain electron microscopy. The images obtained revealed the following phenomena. (i) Crystal-containing elongated vesicles appeared at ≤1.4 µM Ca2+ and almost disappeared at ≥18 µM Ca2+, where ATPase activity reaches its maximum. (ii) At ≥18 µM Ca2+, almost all SR vesicles were in the round form and covered by tightly clustered ATPase crystal patches. (iii) Round vesicles dried on electron microscopy grids occasionally had cracks, probably because surface tension crushed the solid three-dimensional spheres. (iv) [Ca2+]-dependent ATPase crystallization was rapid (<1 min) and reversible. These data prompt the hypothesis that SR vesicles autonomously elongate or contract with the help of a calcium-sensitive ATPase network/endoskeleton and that ATPase crystallization may modulate physical properties of the SR architecture, including the ryanodine receptors that control muscle contraction.
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Affiliation(s)
- Jun Nakamura
- Health and Medical Institute, National Institute of Advanced Industrial Science and Technology, Central 6, 1-1-4 Umezono, Tsukuba 305-8568, Japan
| | - Yuusuke Maruyama
- Health and Medical Institute, National Institute of Advanced Industrial Science and Technology, Central 6, 1-1-4 Umezono, Tsukuba 305-8568, Japan
| | - Genichi Tajima
- Institute for Excellence in Higher Education, Tohoku University, 41 Kawauchi, Aoba-ku, Sendai 980-8576, Japan
| | - Satoshi Hayakawa
- Division of Microbiology, Department of Pathology and Microbiology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi, Tokyo 173-8610, Japan
| | - Makiko Suwa
- Biological Science Course, Graduate School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuou-ku, Sagamihara 252-5258, Japan
| | - Chikara Sato
- Division of Microbiology, Department of Pathology and Microbiology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi, Tokyo 173-8610, Japan
- Biological Science Course, Graduate School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuou-ku, Sagamihara 252-5258, Japan
- Division of Immune Homeostasis, Department of Pathology and Microbiology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi, Tokyo 173-8610, Japan
- School of Integrative and Global Majors (SIGMA), University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
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Elongation and Contraction of Scallop Sarcoplasmic Reticulum (SR): ATP Stabilizes Ca 2+-ATPase Crystalline Array Elongation of SR Vesicles. Int J Mol Sci 2022; 23:ijms23063311. [PMID: 35328731 PMCID: PMC8954933 DOI: 10.3390/ijms23063311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 03/07/2022] [Accepted: 03/10/2022] [Indexed: 02/06/2023] Open
Abstract
The Ca2+-ATPase is an integral transmembrane Ca2+ pump of the sarcoplasmic reticulum (SR). Crystallization of the cytoplasmic surface ATPase molecules of isolated scallop SR vesicles was studied at various calcium concentrations by negative stain electron microscopy. In the absence of ATP, round SR vesicles displaying an assembly of small crystalline patches of ATPase molecules were observed at 18 µM [Ca2+]. These partly transformed into tightly elongated vesicles containing ATPase crystalline arrays at low [Ca2+] (≤1.3 µM). The arrays were classified as ‘’tetramer’’, “two-rail” (like a railroad) and ‘’monomer’’. Their crystallinity was low, and they were unstable. In the presence of ATP (5 mM) at a low [Ca2+] of ~0.002 µM, “two-rail” arrays of high crystallinity appeared more frequently in the tightly elongated vesicles and the distinct tetramer arrays disappeared. During prolonged (~2.5 h) incubation, ATP was consumed and tetramer arrays reappeared. A specific ATPase inhibitor, thapsigargin, prevented both crystal formation and vesicle elongation in the presence of ATP. Together with the second part of this study, these data suggest that the ATPase forms tetramer units and longer tetramer crystalline arrays to elongate SR vesicles, and that the arrays transform into more stable “two-rail” forms in the presence of ATP at low [Ca2+].
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Almeida WI, Martins OB, Carvalho-Alves PC. Self-association of isolated large cytoplasmic domain of plasma membrane H+ -ATPase from Saccharomyces cerevisiae: role of the phosphorylation domain in a general dimeric model for P-ATPases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1768-76. [PMID: 17026955 DOI: 10.1016/j.bbamem.2006.08.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Revised: 08/21/2006] [Accepted: 08/22/2006] [Indexed: 10/24/2022]
Abstract
Large cytoplasmic domain (LCD) plasma membrane H+ -ATPase from S. cerevisiae was expressed as two fusion polypeptides in E. coli: a DNA sequence coding for Leu353-Ileu674 (LCDh), comprising both nucleotide (N) and phosphorylation (P) domains, and a DNA sequence coding for Leu353-Thr543 (LCDDeltah, lacking the C-terminus of P domain), were inserted in expression vectors pDEST-17, yielding the respective recombinant plasmids. Overexpressed fusion polypeptides were solubilized with 6 M urea and purified on affinity columns, and urea was removed by dialysis. Their predicted secondary structure contents were confirmed by CD spectra. In addition, both recombinant polypeptides exhibited high-affinity 2',3'-O-(2,4,6-trinitrophenyl)adenosine-5'-triphosphate (TNP-ATP) binding (Kd = 1.9 microM and 2.9 microM for LCDh and LCDDeltah, respectively), suggesting that they have native-like folding. The gel filtration profile (HPLC) of purified LCDh showed two main peaks, with molecular weights of 95 kDa and 39 kDa, compatible with dimeric and monomeric forms, respectively. However, a single elution peak was observed for purified LCDDeltah, with an estimated molecular weight of 29 kDa, as expected for a monomer. Together, these data suggest that LCDh exist in monomer-dimer equilibrium, and that the C-terminus of P domain is necessary for self-association. We propose that such association is due to interaction between vicinal P domains, which may be of functional relevance for H+ -ATPase in native membranes. We discuss a general dimeric model for P-ATPases with interacting P domains, based on published crystallography and cryo-electron microscopy evidence.
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Affiliation(s)
- W I Almeida
- Instituto de Bioquímica Médica, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-590, Brazil.
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Ryan C, Stokes DL, Chen M, Zhang Z, Hardwicke PMD. Effect of orthophosphate, nucleotide analogues, ADP, and phosphorylation on the cytoplasmic domains of Ca(2+)-ATPase from scallop sarcoplasmic reticulum. J Biol Chem 2003; 279:5380-6. [PMID: 14645252 DOI: 10.1074/jbc.m310085200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The effects of orthophosphate, nucleotide analogues, ADP, and covalent phosphorylation on the tryptic fragmentation patterns of the E1 and E2 forms of scallop Ca-ATPase were examined. Sites preferentially cleaved by trypsin in the E1 form of the Ca-ATPase were detected in the nucleotide (N) and phosphorylation (P) domains, as well as the actuator (A) domain. These sites were occluded in the E2 (Ca(2+)-free) form of the enzyme, consistent with mutual protection of the A, N, and P domains through their association into a clustered structure. Similar protection of cytoplasmic Ca(2+)-dependent tryptic cleavage sites was observed when the catalytic binding site for substrate on the E1 form of scallop Ca-ATPase was occupied by Pi, AMP-PNP, AMP-PCP, or ADP despite the presence of saturating levels of Ca2+. These results suggest that occupation of the catalytic site on E1 can induce condensation of the cytoplasmic domains to yield a unique structural intermediate that may be related to the form of the enzyme in which the active site is prepared for phosphoryl transfer. The effect of Pi on the E2 form of the scallop Ca-ATPase was also investigated, when it was found that formation of E2-P led to extreme resistance toward secondary cleavage by trypsin and stabilization of enzymatic activity for long periods of time.
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Affiliation(s)
- Chris Ryan
- Department of Biochemistry and Molecular Biology, Southern Illinois University, Carbondale, Illinois 62901, USA
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Landeira-Fernandez A. Ca(2+)transport by the sarcoplasmic reticulum Ca(2+)-ATPase in sea cucumber (Ludwigothurea grisea) muscle. J Exp Biol 2001; 204:909-21. [PMID: 11171414 DOI: 10.1242/jeb.204.5.909] [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: 11/20/2022]
Abstract
In muscle cells, the excitation-contraction cycle is triggered by an increase in the concentration of free cytoplasmic Ca(2+). The Ca(2+)-ATPase present in the membrane of the sarcoplasmic reticulum (SR) pumps Ca(2+) from the cytosol into this intracellular compartment, thus promoting muscle relaxation. The microsomal fraction derived from the longitudinal smooth muscle of the body wall from the sea cucumber Ludwigothurea grisea retains a membrane-bound Ca(2+)-ATPase that is able to transport Ca(2+) mediated by ATP hydrolysis. Immunological analyses reveal that monoclonal antibodies against sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA1 and SERCA2a) cross-react with a 110 kDa band, indicating that the sea cucumber Ca(2+)-ATPase is a SERCA-type ATPase. Like the mammalian Ca(2+)-ATPase isoforms so far described, the enzyme also shows a high affinity for Ca(2+) and ATP, has an optimum pH of approximately 7.0 and is sensitive to thapsigargin and cyclopiazonic acid, specific inhibitors of the SERCA pumps. However, unlike the mammalian SERCA isoforms, concentrations of ATP above 2 mmol l(−1) inhibit Ca(2+) transport, but not ATP hydrolysis, in sea cucumber vesicles, suggesting that high ATP concentrations uncouple the Ca(2+)-ATPase. Another unique feature observed with the sea cucumber Ca(2+)-ATPase is the high dependence of maximal activity on K(+) or Na(+). Similar activation promoted by these cations was observed with various mammalian Ca(2+)-ATPase preparations when they were incubated in the presence of low concentrations of sulphated polysaccharides. In control experiments, K(+) and Na(+) have almost no effect on Ca(2+) transport, but in the presence of heparin or fucosylated chondroitin sulphate, the activity of the different mammalian Ca(2+)-ATPases is inhibited and they are activated by either K(+) or Na(+) in a manner similar to the native sea cucumber ATPase. These results led us to investigate the possible occurrence of a highly sulphated polysaccharide on vesicles from the SR of sea cucumber smooth muscle that could act as an ‘endogenous’ Ca(2+)-ATPase inhibitor. In fact, SR vesicles derived from the sea cucumber, but not from rabbit muscle, contain a highly sulphated polysaccharide. After extraction and purification of these polysaccharide molecules, their effect was tested on vesicles obtained from rabbit muscle. This compound inhibited Ca(2+) uptake in rabbit SR vesicles, at concentrations lower than heparin, and restored the dependence on monovalent cations. These results strongly suggest that the sea cucumber Ca(2+)-ATPase is activated by monovalent cations because of the presence of endogenous sulphated polysaccharides.
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Affiliation(s)
- A Landeira-Fernandez
- Instituto de Ciências Biomédicas, Departamento de Bioquímica Médica, Universidade Federal do Rio de Janeiro, UFRJ, Cidade Universitária, RJ, Rio de Janeiro, Brasil 21941-590.
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Chen M, Zhang Z, Tawiah-Boateng MA, Hardwicke PM. A Ca2+-dependent tryptic cleavage site and a protein kinase A phosphorylation site are present in the Ca2+ regulatory domain of scallop muscle Na+-Ca2+ exchanger. J Biol Chem 2000; 275:22961-8. [PMID: 10816565 DOI: 10.1074/jbc.m001743200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Digestion of scallop muscle membrane fractions with trypsin led to release of soluble polypeptides derived from the large cytoplasmic domain of a Na(+)-Ca(2+) exchanger. In the presence of 1 mm Ca(2+), the major product was a peptide of approximately 37 kDa, with an N terminus corresponding to residue 401 of the NCX1 exchanger. In the presence of 10 mm EGTA, approximately 16- and approximately 19-kDa peptides were the major products. Polyclonal rabbit IgG raised against the 37-kDa peptide also bound to the 16- and 19-kDa soluble tryptic peptides and to a 105-110-kDa polypeptide in the undigested membrane preparation. The 16-kDa fragment corresponded to the N-terminal part of the 37-kDa peptide. The conformation of the precursor polypeptide chain in the region of the C terminus of the 16-kDa tryptic peptide was thus altered by the binding of Ca(2+). Phosphorylation of the parent membranes with the catalytic subunit of protein kinase A and [gamma-(32)P]ATP led to incorporation of (32)P into the 16- and 37-kDa soluble fragments. A site may exist within the Ca(2+) regulatory domain of a scallop muscle Na(+)-Ca(2+) exchanger that mediates direct modulation of secondary Ca(2+) regulation by cAMP.
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Affiliation(s)
- M Chen
- Department of Biochemistry and Molecular Biology, Southern Illinois University, Carbondale, Illinois 62901-4413, USA
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Landeira-Fernandez AM, Galina A, Jennings P, Montero-Lomeli M, de Meis L. Sarcoplasmic reticulum Ca(2+)-ATPase of sea cucumber smooth muscle: regulation by K(+) and ATP. Comp Biochem Physiol A Mol Integr Physiol 2000; 126:263-74. [PMID: 10936766 DOI: 10.1016/s1095-6433(00)00197-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Although several Ca(2+)-ATPase isoforms have been described in vertebrates, little is known about Ca(2+)-transport in the muscle of invertebrates. In the microsomal fraction obtained from the sea cucumber (Ludwigothurea grisea) longitudinal body wall smooth muscle, we identified a Ca(2+)-transport ATPase that is able to transport Ca(2+) at the expense of ATP hydrolysis. This enzyme has a high affinity for both Ca(2+) and ATP, an optimum pH around 7.0, and - different from the vertebrate sarcoplasmic reticulum Ca(2+)-ATPases isoforms so far described - is activated 3- to 5-fold by K(+) but not by Li(+), at all temperatures, Ca(2+) and ATP concentrations tested. Calcium accumulation by the sea cucumber microsomes is inhibited by Mg/ATP concentrations >1 mM and the accumulated Ca(2+) is released to the medium when the ATP concentration is raised from 0.1 to 4.0 mM.
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Affiliation(s)
- A M Landeira-Fernandez
- Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Cidade Universitária, 21941-590, Rio de Janeiro, Brazil
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8
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Shi X, Chen M, Huvos PE, Hardwicke PM. Amino acid sequence of a Ca(2+)-transporting ATPase from the sarcoplasmic reticulum of the cross-striated part of the adductor muscle of the deep sea scallop: comparison to serca enzymes of other animals. Comp Biochem Physiol B Biochem Mol Biol 1998; 120:359-74. [PMID: 9787799 DOI: 10.1016/s0305-0491(98)10025-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The RT PCR approach was used to obtain the nucleotide sequence of the mRNA of a sarco/endoplasmic reticulum calcium transporting ATPase (SERCA) from the cross-striated (phasic) part of the adductor muscle of the deep sea scallop. Initially, degenerate primers based on consensus sequences among SERCAs and tryptic fragments of the scallop Ca-ATPase were used. The sequence was then extended using homologous primers and the 5' and 3' ends of the transcript determined by 5' and 3' RACE. The mRNA codes for a polypeptide chain 994 amino acid residues long (coded for by 2982 nucleotides) and has a 195 bp 5' untranslated region, with a 697 bp 3' untranslated region. The scallop enzyme shows strongest amino acid similarity to the SERCA enzyme of Loligo, followed by those of Drosophila and Artemia. It resembles the vertebrate SERCA3 in that it does not possess the phospholamban binding motif and so is unlikely to be regulated by protein kinase A mediated signals.
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Affiliation(s)
- X Shi
- Southern Illinois University, Carbondale 62901-4413, USA
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Nagata Y, Yamamoto T, Ema M, Mimura J, Fujii-Kuriyama Y, Suzuki T, Furukohri T, Konishi K, Sato D, Tajima G, Nakamura J. cDNA cloning and predicted primary structure of scallop sarcoplasmic reticulum Ca(2+)-ATPase. Comp Biochem Physiol B Biochem Mol Biol 1998; 119:777-85. [PMID: 9787769 DOI: 10.1016/s0305-0491(98)00055-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sarcoplasmic reticulum (SR) Ca(2+)-ATPase of the scallop cross-striated adductor muscle was purified with deoxycholate and digested with lysyl endopeptidase for sequencing of the digested fragments. Overlapping cDNA clones of the ATPase were isolated by screening the cDNA library with an RT-PCR product as a hybridization probe, which encodes the partial amino acid sequence of the ATPase. The predicted amino acid sequence of the ATPase contained all the partial sequences determined with the proteolytic fragments and consisted of the 993 residues with approximately 70% overall sequence similarity to those of the SR ATPases from rabbit fast-twitch and slow-twitch muscles. An outline of the structure of the scallop ATPase molecule is predicted to mainly consist of ten transmembrane and five 'stalk' domains with two large cytoplasmic regions as observed with the rabbit ATPase molecules. The sequence relationship between scallop and other sarco/endoplasmic reticulum-type Ca(2+)-ATPases is discussed.
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Affiliation(s)
- Y Nagata
- Biological Institute, Graduate School of Science, Osaka University, Japan
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Burlando B, Viarengo A, Pertica M, Ponzano E, Orunesu M. Effects of free oxygen radicals on Ca2+ release mechanisms in the sarcoplasmic reticulum of scallop (Pecten jacobaeus) adductor muscle. Cell Calcium 1997; 22:83-90. [PMID: 9292226 DOI: 10.1016/s0143-4160(97)90108-1] [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: 02/05/2023]
Abstract
In vitro oxyradical effects on SR Ca2+ regulation were studied by using a SR-containing cell-free preparation from scallop (Pecten jacobaeus) adductor muscle. Ca2+ variations were fluorimetrically detected after incubation with Fluo-3 in the presence of ATP. Exposure to Fe3+/ascorbate produced dose-dependent Ca2+ release from SR vesicles, eventually leading to massive Ca2+ loss. Exposure to hypoxanthine/xanthine oxidase also caused Ca2+ release but at a much slower rate. Pre-incubations with catalase or with the hydroxyl radical scavenger KMBA led to a significant decrease in the Fe3+/ascorbate-induced Ca2+ release rate and to a delay of massive Ca2+ loss. Pre-incubations with GSH or DTT strongly reduced the Ca2+ release caused by Fe3+/ascorbate and, moreover, they prevented massive Ca2+ loss from SR vesicles. Addition of GSH or DTT after Fe3+/ascorbate promptly reduced the Ca2+ release rate and delayed massive Ca2+ release. Pre-incubation with the SR Ca2+ channel blocker ruthenium red strongly reduced the Ca2+ release caused by Fe3+/ascorbate, and also prevented massive Ca2+ loss. In the presence of ruthenium red, Fe3+/ascorbate treatments followed by Ca2+ addition revealed that Ca2+ uptake inhibition was slower than Ca2+ release. Taken together, data showed that free radicals and, in particular, hydroxyl radicals, affected the scallop SR Ca2+ regulation. This mainly occurred through Ca2+ channel opening, most likely triggered by sulfhydryl oxidation, which eventually led to massive Ca2+ release from SR vesicles. The demonstration of a specific effect of oxyradicals on SR Ca2+ channels is in line with their possible involvement in cell signaling.
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Affiliation(s)
- B Burlando
- Dipartimento di Scienze e Tecnologie Avanzate, Università di Torino, Alessandria, Italy.
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Karon BS, Thomas DD. Molecular mechanism of Ca-ATPase activation by halothane in sarcoplasmic reticulum. Biochemistry 1993; 32:7503-11. [PMID: 8393342 DOI: 10.1021/bi00080a023] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We have studied the molecular mechanism of Ca-ATPase activation in sarcoplasmic reticulum (SR) by the volatile anesthetic halothane. Using time-resolved phosphorescence anisotropy, we determined the rotational correlation times and mole fractions of different oligomeric states of the enzyme, as a function of halothane and temperature. Lipid fluidity was measured independently, using EPR of spin-labeled lipids. At 4 and 7 degrees C, the principal effects of halothane were to increase the activity of the Ca-ATPase and to promote the formation of monomers and dimers of the enzyme from larger aggregates. At higher temperatures (up to 25 degrees C), halothane activated the enzyme, but to a lesser extent than observed at lower temperatures. While the functional effects of halothane were temperature dependent, the effects of halothane on lipid fluidity and protein aggregation state were similar at all temperatures tested. We conclude that at low temperatures Ca-ATPase activity is dominated by aggregation state, so halothane activates the enzyme primarily by promoting the formation of monomers and dimers of the enzyme from larger aggregates. At higher temperatures, the activity of the enzyme is dominated by lipid fluidity, so halothane activates the enzyme by increasing the lipid fluidity. The physical mechanism of Ca-ATPase activation, dominated by aggregation state at low temperature and lipid fluidity at higher temperature, provides an explanation for the break in the Arrhenius plot of Ca-ATPase activity (in the absence of halothane) at approximately 20 degrees C.
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Affiliation(s)
- B S Karon
- Department of Biochemistry, University of Minnesota Medical School, Minneapolis 55455
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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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