Ouabain-resistant transfectants of the murine ouabain resistance gene contain mutations in the alpha-subunit of the Na,K-ATPase.

17β-O-Aminoalkyloximes of 5β-Androstane-3β,14β-diol with Digitalis-like Activity: Synthesis, Cardiotonic Activity, Structure−Activity Relationships, and Molecular Modeling of the Na+,K+-ATPase Receptor

“…In particular, the greatest ouabain resistance is given by substitutions in the extracellular loop, such as Gln111Arg, Asp121(Gly, Glu), or Asn122Asp, 21,22 or Gln118Arg and Asp129Asn in Torpedo electroplax, 23 as well as those involving the hydrophobic core of the transmembrane region, such as Cys104(Ala, Phe) or Tyr108Ala, 24 or Tyr124Cys or Ile135Val. 25 A specific role for Cys104 was established, with a putative hydrogen-bond formation with the lactone ring. On this basis, Repke et al 6,26,27 proposed Although there is substantial agreement in the literature about the length and position of the transmembrane domains (Phe93-Ile110 and Leu123-Ser140 for H1 and H2, respectively, with the connecting loop mainly composed of hydrophilic residues), no information is at present available on the molecular structure of any ATPase R1-subunit at the atomic level nor on the relative orientation of H1 with respect to H2.…”

“…Comprehensive random mutagenesis studies and photoaffinity labeling showed that most of the amino acid substitutions conferring ouabain-resistance relate to the H1−H2 region of the Na + ,K + -ATPase α 1-subunit. In particular, the greatest ouabain resistance is given by substitutions in the extracellular loop, such as Gln111Arg, Asp121(Gly, Glu), or Asn122Asp, , or Gln118Arg and Asp129Asn in Torpedo electroplax , as well as those involving the hydrophobic core of the transmembrane region, such as Cys104(Ala, Phe) or Tyr108Ala, or Tyr124Cys or Ile135Val . A specific role for Cys104 was established, with a putative hydrogen-bond formation with the lactone ring.…”