Human placental Na+,K+-ATPase alpha subunit: cDNA cloning, tissue expression, DNA polymorphism, and chromosomal localization.

A 2.2-kilobase clone comprising a major portion of the coding sequence of the Na+,K+-ATPase alpha subunit was cloned from human placenta and its sequence was identical to that encoding the alpha subunit of human kidney and HeLa cells. Transfer blot analysis of the mRNA products of the Na+,K+-ATPase gene from various human tissues and cell lines revealed only one band (approximately 4.7 kilobases) under low and high stringency washing conditions. The levels of expression in the tissues were intestine greater than placenta greater than liver greater than pancreas, and in the cell lines the levels were human erythroleukemia greater than butyrate-induced colon greater than colon greater than brain greater than HeLa cells. mRNA was undetectable in reticulocytes, consistent with our failure to detect positive clones in a size-selected (greater than 2 kilobases) lambda gt11 reticulocyte cDNA library. DNA analysis revealed a polymorphic EcoRI band and chromosome localization by flow sorting and in situ hybridization showed that the alpha subunit is on the short arm (band p11-p13) of chromosome 1.