Cardiac Sarcoplasmic Reticulum Ca
            <sup>2+</sup>
            ‐
            <scp>ATPase</scp>

Tada, Michihiko; Toyofuku, Toshihiko

doi:10.1002/cphy.cp020108

Cited by 6 publications

(7 citation statements)

References 298 publications

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“…During Ca 2+ -dependent hydrolysis of ATP by the cardiac SR vesicles, the terminal phosphate ( -[P]) of ATP is incorporated into the ATPase protein, forming a phospho-enzyme intermediate denoted by EP. 1 The formation of EP is measured by the incorporation of 32 P from [ -32 P]ATP into a trichloroacetic acid (TCA)precipitate of SR or Ca 2+ -ATPase protein. The maximum amount of phosphoenzyme formed, which reflects the amount of ATPase protein in a typical preparation of cardiac SR, is up to 1.3 mmoles/mg protein.…”

Section: Mechanism Of Ca 2+ -Atpase Activity and Ca 2+ -Pumping Functionmentioning

confidence: 99%

“…These rates parallel each other under various conditions, indicating that they are tightly coupled. A number of experimental findings in skeletal muscle SR vesicles (SERCA1) confirm that 1 mole of Ca 2+ -ATPase transports 2 moles of Ca 2+ ions from the cytoplasm to the luminal space at the expense of 1 mole of ATP hydrolyzed, 1,13,14 indicating that the stoichiometric ratio between Ca 2+ transported and ATP hydrolyzed is 2:1. These findings are in accord with the predicted model of SERCA1, 14,15 based upon mutagenesis data, that the Ca 2+ -binding cavity formed by the transmembrane helices M4, M5, and M6 would bind 2 Ca 2+ ions.…”

Section: Mechanism Of Ca 2+ -Atpase Activity and Ca 2+ -Pumping Functionmentioning

confidence: 99%

“…Three Cys residues (Cys 36 , Cyc 41 , and Cys 46 ), which lie at every 5 residues in an -helix, exist as free SH groups rather than forming disulfide bonds during pentamer formation. 1 It was predicted that the hydrophobic residues form a 3.5 residue/turn helix, 1 which allowed construction of a model of the interacting surfaces in which the helices are associated in a lefthanded pentameric coiled configuration. Mutation of the hydrophobic residues Ile 40 , Leu 43 , and Ile 47 destabilizes the pentamer, consistent with the view that these residues are critical to homo-pentameric formation.…”

Section: Moleular Structure Of Phospholambanmentioning

confidence: 99%

“…42 These effects of catecholamines on myocardial cell contractility are considered to result from cAMP and PKA effects on Ca 2+ fluxes across the SR and sarcolemmal membranes of myocardial cells. 1 Ca 2+ flux through Ca 2+ channels in the sarcolemmal membrane is activated by PKA. 1 This 'trigger' Ca 2+ accelerates Ca 2+ -induced Ca 2+ release from SR, thus increasing the rate and extent of myofibrillar contraction.…”

Section: Physiological and Pathophysiological Relevance Of The Pln -Smentioning

confidence: 99%

“…1 Ca 2+ flux through Ca 2+ channels in the sarcolemmal membrane is activated by PKA. 1 This 'trigger' Ca 2+ accelerates Ca 2+ -induced Ca 2+ release from SR, thus increasing the rate and extent of myofibrillar contraction. The onset of increased tension after exposure of the heart to catecholamines is gradual, reaching the steady state after approximately 20 beats.…”

Section: Physiological and Pathophysiological Relevance Of The Pln -Smentioning

confidence: 99%

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Calcium Cycling Proteins of the Cardiac Sarcoplasmic Reticulum-Molecular Regulation of the Phospholamban-SERCA Ca2+ Pump System and Its Pathophysiological Consequences-

Tada

2003

Circ J

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he sarcoplasmic reticulum (SR) is a tubular, membranous network within muscle cells, which is the analogue of the endoplasmic reticulum (ER) in other cells. This organelle has a variety of functions, of which release of Ca 2+ to the cytosol and reuptake into the interior compartment (the lumen) of the SR are the most important. Rapid release of Ca 2+ through a Ca 2+ release channel (ryanodine receptor) in the skeletal muscle SR is responsible for muscle contraction: reuptake of Ca 2+ by the action of a Ca 2+ -ATPase is responsible for muscle relaxation. In cardiac muscle, however, the intracellular Ca 2+ concentration is controlled not only by the SR, but also by other pumps, channels, and exchangers located in the sarcolemma/T-tubules. Nonetheless, the SR of mammalian cardiac cells is well developed and has a major role in the EC coupling. 1,2 In the SR of cardiac muscle, as well as in slow-twitch skeletal and smooth muscles, phospholamban (PLN) participates in the EC coupling processes by regulating the activity of the Ca 2+ -ATPase. Of particular interest is the molecular mode of PLN-mediated regulation of SR Ca 2+ -ATPase, in which cAMP-dependent protein kinase (PKA)-catalyzed phosphorylation of PLN results in marked augmentation of the Ca 2+ -ATPase activity. 1,3 The molecular structure and function of the 2 important proteins in cardiac SR are highlighted in this review: Ca 2+ -ATPase and PLN and their molecular interactions, which would help understand the positive and negative inotropic effects of -adrenergic agonist/antagonist. The pathophysiological consequences of molecular perturbation of such a system are also briefly mentioned, leading to an evolving notion that 'calcium cycling defects' underlie cardiac hypertrophy and failure.Since MacLennan first purified Ca 2+ -ATPase from detergent-solubilized SR vesicles from rabbit skeletal muscle, 6 extensive efforts have been made to sequence the Ca 2+ -ATPase protein, but only with partial success. Molecular cloning of full-length cDNAs encoding all 3 SERCA iso- J 2003; 67: 729 -737 Circ

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Section: Mechanism Of Ca 2+ -Atpase Activity and Ca 2+ -Pumping Functionmentioning

confidence: 99%