The crustacean gill (Na+,K+)-ATPase: Allosteric modulation of high- and low-affinity ATP-binding sites by sodium and potassium
| Autor: | Rosa dos Prazeres Melo Furriel, D. C. Masui, Fernando Luis Medina Mantelatto, Helena M. Scofano, E. C. C. Silva, John Campbell McNamara, Hector Barrabin, Carlos Frederico Leite Fontes, Francisco de Assis Leone |
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| Rok vydání: | 2008 |
| Předmět: |
animal structures
Brachyura ATPase Sodium Allosteric regulation Biophysics chemistry.chemical_element Biochemistry Catalysis Adenosine Triphosphate Osmotic Pressure Animals Phosphorylation Na+/K+-ATPase Binding site Molecular Biology chemistry.chemical_classification Binding Sites Ion Transport biology Euryhaline Enzyme chemistry Vertebrates biology.protein Saturation vapor curve Sodium-Potassium-Exchanging ATPase Protein Binding |
| Zdroj: | Archives of Biochemistry and Biophysics. 479:139-144 |
| ISSN: | 0003-9861 |
| Popis: | The blue crab, Callinectes danae, tolerates exposure to a wide salinity range employing mechanisms of compensatory ion uptake when in dilute media. Although the gill (Na+,K+)-ATPase is vital to hyperosmoregulatory ability, the interactions occurring at the sites of ATP binding on the molecule itself are unknown. Here, we investigate the modulation by Na+ and K+ of homotropic interactions between the ATP-binding sites, and of phosphoenzyme formation of the (Na+,K+)-ATPase from the posterior gills of this euryhaline crab. The contribution of the high- and low-affinity ATP-binding sites to maximum velocity was similar for both Na+ and K+. However, in contrast to Na+, a threshold K+ concentration triggers the appearance of the high-affinity binding sites, displacing the saturation curve to lower ATP concentrations.Further, a low-affinity site for phosphorylation is present on the enzyme. These findings reveal notable differences in the catalytic mechanism of the crustacean (Na+,K+)-ATPase compared to the vertebrate enzyme. |
| Databáze: | OpenAIRE |
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