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1984 (1)
1982 (2)
1Author    Charles Tanford, DwightW. MartinRequires cookie*
 Title    Equilibrium Constants for Some Steps of the Reaction Cycle of the Sarcoplasmic Reticulum Calcium Pump  
 Abstract    This paper summarizes true equilibrium m easurements for som e partial reactions o f the sar­ coplasmic reticulum calcium pum p transport cycle. The most important result is the estim ation o f the equilibrium constant for the interconversion o f the two major conformational states o f the protein, E (Ca2+ binding sites facing the cytoplasm) and E' (C a2+ binding sides facing the sar­ coplasm ic reticulum lumen). The value o f K0 = [E']/[E] cannot be evaluated directly by any method available at present, but observed cooperativity in the binding o f Mg2+ and Ca2+ to un-liganded protein strongly indictes that K0 ^ 1-The m ost probable value, valid within an order o f magnitude, is K0 ~ 103, i.e., the E' state is more stable than the E state by about 4 kcal/m ol. 
  Reference    Z. Naturforsch. 37c, 522 (1982); received February 19 1982 
  Published    1982 
  Keywords    Ca2+ ATPase, Free Energy Transduction, Active Transport 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0522.pdf 
 Identifier    ZNC-1982-37c-0522 
 Volume    37 
2Author    Angela De, Souza Otero, Leopoldo De MeisRequires cookie*
 Title    Phosphorylation o f Ca2+-ATPase by Inorganic Phosphate in Water-Organic Solvent Media: Dielectric Constant and Solvent Hydrophobicity Contribution1  
 Abstract    The effect o f organic solvents on the phosphorylation o f the Ca2+-dependent ATPase o f sar­ coplasmic reticulum by inorganic phosphate in the absence o f a calcium gradient was investi­ gated. Kinetic analysis o f the reaction in water and water-organic solvent m edia according to a bireactant scheme shows no correlation betw een changes in kinetic parameters and the dieletric constant o f the mixed solvents. The pronounced increase in equilibrium levels o f phosphoenzym e in water-solvent mixtures is attributed to changes in the water activity o f the m edium. 
  Reference    Z. Naturforsch. 37c, 527 (1982); received January 4 1982 
  Published    1982 
  Keywords    Phosphorylation, Ca2+-ATPase, Inorganic Phosphate, O rganic Solvents 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0527.pdf 
 Identifier    ZNC-1982-37c-0527 
 Volume    37 
3Author    N. Ald, J. Scales, StefanR H IghsmRequires cookie*
 Abstract    lec tr o n M ic r o sc o p ic E vid en ce fo r th e T ran sm em b ran e D isp la ce m e n t o f C alcium A T P a se Incubation o f the Ca2+-ATPase in vanadate solutions leads to the formation o f two-dim ensional arrays in the sarcoplasmic reticulum membrane. Electron micrographic freeze fracture replicas show depressions on the inner leaflet for the first time. This indicates that the ATPase has moved perpendicular to the plane o f the m embrane. Our results also suggest that aggregation o f the Ca2+-ATPase into the two-dim ensional arrays occurs before they move into the membrane. These phenom ena were observed as soon as 15 minutes after vanadate was added. The effects o f vanadate appear to be com pletely reversible. When SR was incubated in the vanadate solutions and was then diluted into a buffer containing Ca2+ and ATP, the ATPase activity was normal for up to several hours o f incubation and only somewhat reduced after 3 days. 
  Reference    Z. Naturforsch. 39c, 177 (1984); received May 30/Septem ber 29 1983 
  Published    1984 
  Keywords    Sarcoplasmic Reticulum, Ca2+-ATPase, Ion Transport, Vanadate 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0177_n.pdf 
 Identifier    ZNC-1984-39c-0177_n 
 Volume    39