title: Tb3+ binding to human erythrocyte spectrin resulting in conformation change and aggregation.
abstract: The Tb3+ binding to spectrin tetramer (SPT) was studied by Tb3+ fluorescence titration and CD spectra. The results indicated that the total high-affinity Tb3+ binding sites are n1 = 330, with average Kd = 3.6 x 10(-6) M. Among them, ca. 90 sites are of higher affinity and are probably more specific to Tb3+ than the remaining sites. There are 520 low affinity Tb3+ binding sites with average Kd = 1.5 x 10(-5) M. Fluorescence and CD spectra revealed that the alpha-helix content of SPT decreased with Tb3+ binding to specific sites and further binding did not result in conformation change. Tb3+ binding to SPT and the subsequent reactions were studied by employing stopped-flow fluorescence and light scattering methods. The studies demonstrate that this is a multistep reaction assembly: high-affinity terbium binding-conformation change-aggregation-low-affinity terbium binding--the second conformation change. The critical Tb3+ concentration-induced spectrin dimer (SPD) aggregation was determined with a light scattering method.
authors.affiliation: Inorganic Chemistry Department, Beijing Medical University, China.
authors.forename: H Y
authors.initials: HY
authors.lastname: Sun
authors.forename: H
authors.initials: H
authors.lastname: Lin
authors.forename: Y
authors.initials: Y
authors.lastname: Cao
authors.forename: R
authors.initials: R
authors.lastname: Li
authors.forename: K
authors.initials: K
authors.lastname: Wang
authors.forename: R
authors.initials: R
authors.lastname: Chen
mesh_terms: D001665:Binding Sites; D006801:Humans; D007700:Kinetics; D008027:Light; D011108:Polymers; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012542:Scattering, Radiation; D013049:Spectrin / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013725:Terbium / Q000378:metabolism*
chemical_list: D011108:Polymers; D013725:Terbium; D013049:Spectrin