title: Anion interactions with Na,K-ATPase: simultaneous binding of nitrate and eosin.
abstract: Nucleotide binding affinity to Na,K-ATPase is reduced by a number of anions such as nitrate and perchlorate in comparison with affinity in the presence of chloride (all with sodium as the cation). The reduction correlates with the position of these anions in the Hofmeister series. Transient kinetic experiments using the fluorescent dye eosin-which binds to the nucleotide site of the Na,K-ATPase-show that simultaneous anion binding, exemplified with nitrate, and eosin binding is possible. The effect of nitrate on eosin binding is reflected in a decreased binding-rate constant and an increased dissociation rate constant, leading to a decreased equilibrium binding constant for eosin. Since eosin binding is analogous with nucleotide binding to Na,K-ATPase, the results suggest the simultaneous presence of nucleotide and anion binding sites.
authors.affiliation: Department of Biophysics, University of Aarhus, Ole Worms Allé 185, 8000, Aarhus, Denmark. me@biophys.au.dk
authors.forename: Mikael
authors.initials: M
authors.lastname: Esmann
authors.forename: Natalya U
authors.initials: NU
authors.lastname: Fedosova
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry*; D000838:Anions / Q000737:chemistry; D001665:Binding Sites; D004789:Enzyme Activation; D004801:Eosine Yellowish-(YS) / Q000032:analysis / Q000737:chemistry*; D017022:Flow Injection Analysis; D007700:Kinetics; D009566:Nitrates / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D000838:Anions; D009566:Nitrates; D000244:Adenosine Diphosphate; D000254:Sodium-Potassium-Exchanging ATPase; D004801:Eosine Yellowish-(YS)