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XB-ART-36078
Biochem Biophys Res Commun 2007 Apr 27;3561:142-6. doi: 10.1016/j.bbrc.2007.02.119.
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Role of homologous ASP334 and GLU319 in human non-gastric H,K- and Na,K-ATPases in cardiac glycoside binding.

Radkov R , Kharoubi-Hess S , Schaer D , Modyanov NN , Geering K , Horisberger JD .


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Cardiac steroids inhibit Na,K-ATPase and the related non-gastric H,K-ATPase, while they do not interact with gastric H,K-ATPase. Introducing an arginine, the residue present in the gastric H,K-ATPase, in the second extracellular loop at the corresponding position 334 in the human non-gastric H,K-ATPase (D334R mutation) rendered it completely resistant to 2mM ouabain. The corresponding mutation (E319R) in alpha1 Na,K-ATPase produced a approximately 2-fold increase of the ouabain IC(50) in the ouabain-resistant rat alpha1 Na,K-ATPase and a large decrease of the ouabain affinity of human alpha1 Na,K-ATPase, on the other hand this mutation had no effect on the affinity for the aglycone ouabagenin. These results provide a strong support for the orientation of ouabain in its biding site with its sugar moiety interacting directly with the second extracellular loop.

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Species referenced: Xenopus laevis
Genes referenced: atp1a1

References [+] :
Antolovic, Labeling of a cysteine in the cardiotonic glycoside binding site by the steroid derivative HDMA. 1995, Pubmed, Xenbase