title: Ligand binding properties of the sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPase labelled with N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl)carbodiimide.
abstract: The (Ca2+ + Mg2+)-ATPase of rabbit sarcoplasmic reticulum, when labelled at two Ca2+-protected sites with N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl)carbodiimide (NCD-4) retains Ca2+ binding capacity at the sites with Kd values of approx. 3 microM and 0.12 mM as assessed by fluorescence titration. The sites correspond to the two high-affinity Ca2+ binding sites present in the native ATPase. The NCD-4 labelled ATPase exhibits slow conformational changes at each site on addition of Ca2+. It retains the ability to form phosphoenzyme, and can most likely translocate Ca2+.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002234:Carbodiimides / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism*; D007700:Kinetics; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*
chemical_list: D002234:Carbodiimides; D005456:Fluorescent Dyes; D000255:Adenosine Triphosphate; C038088:N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl)carbodiimide; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium