title: Measurement of Ca2+-binding constants of proteins and presentation of the CaLigator software.
abstract: The complexity of Ca2+ cell signaling is dependent on a plethoria of Ca2+-binding proteins that respond to signals in different ranges of Ca2+ concentrations. Since the function of these proteins is directly coupled to their Ca2+-binding properties, there is a need for accurately determined equilibrium Ca2+-binding constants. In this work we outline the experimental techniques available to determine Ca2+-binding constants in proteins, derive the models used to describe the binding, and present CaLigator, software for least-square fitting directly to the measured quantity. The use of the software is illustrated for Ca2+-binding data obtained for two deamidated forms of calbindin D(9k), either an isospartate-56 (beta form) or a normal Asp-56 (alpha form). Here, the Ca2+-binding properties of the two isoforms have been studied using the chelator method. The alpha form shows similar Ca2+-binding properties to the wild type while the beta form has lost both cooperativety and affinity.
authors.affiliation: Department of Biophysical Chemistry, Lund University, Lund, S-221 00, Sweden.
authors.forename: Ingemar
authors.initials: I
authors.lastname: André
authors.forename: Sara
authors.initials: S
authors.lastname: Linse
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D019295:Computational Biology; D007700:Kinetics; D008954:Models, Biological; D011485:Protein Binding; D012984:Software
chemical_list: D002135:Calcium-Binding Proteins; D002118:Calcium