Identification of a region within the Na,K-ATPase alpha subunit that contributes to differential ouabain sensitivity.

To analyze determinants within the Na,K-ATPase alpha subunit that contribute to differential ouabain sensitivity, we constructed and expressed a panel of chimeric cDNA molecules between ouabain-resistant and ouabain-sensitive alpha subunit cDNAs. When introduced into ouabain-sensitive monkey CV-1 cells, ouabain-resistant rat alpha 1 subunit cDNA and chimeras in which the 5' end of ouabain-sensitive human alpha 1 or rat alpha 2 subunit cDNA was replaced by the 5' end of rat alpha 1 subunit cDNA conferred resistance to 100 microM ouabain. Monkey cells transfected with the reciprocal chimeras were unable to survive selection in 1 microM ouabain. Rat alpha 2 subunit cDNA and a chimera in which the 5' end of rat alpha 1 subunit cDNA was replaced by the 5' end of rat alpha 2 subunit cDNA conferred resistance to 0.5 microM ouabain. These results suggest that determinants of ouabain resistance reside within the amino-terminal portions of the rat alpha 1 and alpha 2 subunits. Expression of chimeric alpha subunit cDNAs should prove useful for elucidating the structural basis of Na,K-ATPase function.