The molecular basis for the marked difference between primate and rodent cells in sensitivity to the cardiac glycoside ouabain has been established by genetic techniques. A complementary DNA encoding the entire α1 subunit of the mouse Na+- and K+-dependent adenosine triphosphatase (ATPase) was inserted into the expression vector pSV2. This engineered DNA molecule confers resistance against 10-4 M ouabain to monkey CV-1 cells. Deletion of sequences encoding the carboxyl terminus of the α1 subunit abolish the activity of the complementary DNA. The ability to assay the biological activity of this ATPase in a transfection protocol permits the application of molecular genetic techniques to the analysis of structure-function relationships for the enzyme that establishes the internal Na+/K+ environment of most animal cells. The full-length α1 subunit complementary DNA will also be useful as a dominant selectable marker for somatic cell genetic studies utilizing ouabain-scnsitive cells.
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