title: Ruthenium red affects the intrinsic fluorescence of the calcium-ATPase of skeletal sarcoplasmic reticulum.
abstract: We have studied the effect of Ruthenium red on the sarcoplasmic reticulum Ca(2+)-ATPase. Ruthenium red does not modify the Ca2+ pumping activity of the enzyme, despite its interaction with cationic binding sites on sarcoplasmic reticulum vesicles. Two pools of binding sites were distinguished. One pool (10 nmol/mg) is dependent upon the presence of micromolar Ca2+ and may therefore represent the high-affinity Ca2+ transport sites of the Ca(2+)-ATPase. However, Ruthenium red only slightly competes with Ca2+ on these sites. The other pool (15-17 nmol/mg) is characterized as low-affinity cation binding sites of sarcoplasmic reticulum, distinct from the Mg2+ site involved in the ATP binding to the Ca(2+)-ATPase. The interaction of Ruthenium red with these low-affinity cation binding sites, which may be located either on the Ca(2+)-ATPase or on surrounding lipids, decreases tryptophan fluorescence level of the protein. As much as 25% of the tryptophan fluorescence of the Ca(2+)-ATPase is quenched by Ruthenium red (with a dissociation constant of 100 nM), tryptophan residues located near the bilayer being preferentially affected.
authors.affiliation: Laboratoire de Biophysique Moléculaire et Cellulaire, URA 520 du CNRS, DBMS/LBIO, Centre d'Etudes Nucléaires de Grenoble, France.
authors.forename: M J
authors.initials: MJ
authors.lastname: Moutin
authors.forename: C
authors.initials: C
authors.lastname: Rapin
authors.forename: Y
authors.initials: Y
authors.lastname: Dupont
mesh_terms: D000818:Animals; D001692:Biological Transport; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000737:chemistry*; D002413:Cations, Divalent; D005453:Fluorescence; D008274:Magnesium / Q000378:metabolism; D011817:Rabbits; D012430:Ruthenium Red / Q000494:pharmacology*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects* / Q000201:enzymology
chemical_list: D002413:Cations, Divalent; D012430:Ruthenium Red; D000001:Calcimycin; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D002118:Calcium