These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Lysine 480 is not an essential residue for ATP binding or hydrolysis by Na,K-ATPase.
    Author: Wang K, Farley RA.
    Journal: J Biol Chem; 1992 Feb 25; 267(6):3577-80. PubMed ID: 1310976.
    Abstract:
    Lysine 480 has been suggested to be essential for ATP binding and hydrolysis by Na,K-ATPase because it is labeled by reagents that are thought to react with the ATPase from within the ATP binding site. In order to test this hypothesis, Lys-480 was changed to Ala, Arg, or Glu by site-directed mutagenesis, and the resultant Na,K-ATPase molecules were expressed in yeast cells. The ATPase activity of each of the mutants was similar to the activity of the wild type enzyme indicating that Lys-480 is not essential for ATP hydrolysis. The binding of [3H]ouabain in both ATP-dependent and inorganic phosphate-dependent reactions was used to determine the apparent affinity of each mutant for ATP or Pi. The K0.5(ATP) for ouabain binding to phosphoenzyme formed from ATP was 1-3 microM for Lys-480, Arg-480, and Ala-480, whereas for Glu-480 the K0.5(ATP) was 18 microM. The K0.5(Pi) for ouabain binding to phosphoenzyme formed from inorganic phosphate was 16-28 microM for Lys-480, Arg-480, and Ala-480, but was 74 microM for Glu-480. The Kd for ouabain binding was similar for both the wild type and mutant Na,K-ATPase molecules (3-6 nM). These data indicate that the substitution of an acidic amino acid for lysine at position 480 appears to reduce the affinity of the Na,K-ATPase for both ATP and phosphate. It is concluded that Lys-480 is not essential for ATP binding or hydrolysis or for phosphate binding by Na,K-ATPase but is likely to be located within the ATP binding site of the Na,K-ATPase.
    [Abstract] [Full Text] [Related] [New Search]