title: [Effect of urea on conformational changes in the active site of native and reconstituted Ca-ATPase of the sarcoplasmic reticulum].
abstract: The effect of urea (1-3 M) on conformational changes in the active center of native and reconstituted Ca-ATPase of sarcoplasmic reticulum modified by fluorescein-5-isothiocyanate (FITC) was studied using the method of fluorescence titration by neodymium (Nd3+) ions. Based on the analysis of curves of fluorescence quenching of FITC-labeled Ca-ATPase by Nd3+ ions, the parameters characterizing the structural changes in the Mg-ATP binding center were determined. It was assumed that FITC and Nd3+ ion bind to different polypeptide fragments moving relative to each other, which provides the conformational lability of the nucleotide binding site at some stages of the catalytic cycle. A comparison of structural changes caused by urea at the active site of native and reconstituted Ca-ATPase of sarcoplasmic reticulum indicates that the Nd3+ binding center is localized in the region of contacts of monomers in the oligomer.
authors.affiliation: Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia.
authors.forename: M G
authors.initials: MG
authors.lastname: Vinokurov
authors.forename: M N
authors.initials: MN
authors.lastname: Ivkova
authors.forename: V A
authors.initials: VA
authors.lastname: Pechatnikov
mesh_terms: D000818:Animals; D001665:Binding Sites; D000252:Calcium-Transporting ATPases / Q000737:chemistry*; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D005470:Fluorometry; D009354:Neodymium; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000737:chemistry*; D014508:Urea / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D009354:Neodymium; D014508:Urea; D000252:Calcium-Transporting ATPases; D016650:Fluorescein-5-isothiocyanate
vernacular_title: Vliianie mocheviny na konformatsionnye perestroĭki v aktivnom tsentre nativnoĭ i rekonstruirovannoĭ Ca-ATFazy sarkoplazmaticheskogo retikuluma.