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1989 (1)
1Author    Elisabeth Fassold, Wilhelm Hasselbach, Bernd KüchlerRequires cookie*
 Title    Effect of Non-Solubilizing SDS Concentrations on High Affinity Ca2+ Binding and Steady State Phosphorylation by Inorganic Phosphate of the Sarcoplasmic Reticulum ATPase  
 Abstract    In this investigation low, non-solubilizing concentrations of the strong anionic detergent SDS were used to perturbate the interaction of Ca2+ and P, with their respective binding domains on the sarcoplasmic reticulum Ca-transport ATPase. Rising SDS concentrations produce a two-step decline of Ca2+-dependent ATP hydrolysis. At pH 6.15, SDS differently affects high affinity Ca2+ binding and phosphorylation by inorganic phosphate and releases the "mutual exclusion" of these two ligand binding steps. The degree of uncoupling is considerably more pronounced in the presence of 20% Me2SO. The reduction of Ca2+ binding by SDS is demonstrated to be a result of decreased affinity of one of the two specific high affinity binding sites and of perturbation of their cooperative inter­ action. Higher SDS partially restores the original high Ca2f affinity but not the cooperativity of binding. Phosphorylation exhibits a higher SDS sensitivity than Ca2+ binding: Increasing SDS competitively inhibits and then completely abolishes phosphoenzyme formation. Thus. SDS binds to the phosphorylation domain, evidently involving the Lys352 residue of the ATPase molecule; this is accompanied by a more unspecific concentration-dependent SDS effect, probably mediated by hydrophobic force, which, finally, suppresses phosphorylation. Me2SO does neither qualitatively affect the SDS-dependent chemical properties of the vesicular material nor the SDS-dependent perturbation of the investigated reaction steps. 
  Reference    Z. Naturforsch. 44c, 139 (1989); received November 28 1988 
  Published    1989 
  Keywords    Sarcoplasmic Reticulum ATPase, Calcium Binding, Phosphorylation, SDS 
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 TEI-XML for    default:Reihe_C/44/ZNC-1989-44c-0139.pdf 
 Identifier    ZNC-1989-44c-0139 
 Volume    44