Two Slightly Different α-Subunit Components of Kidney Na,K-ATPase Induced by Heat Treatment

Abstract

This chapter discusses two slightly different α-subunit components of kidney Na, K-ATPase induced by heat treatment. The chemical multiplicity of the α-subunit of Na, K-ATPase is indicated in several vertebrate nervous tissue enzymes and in the α-subunit of the brine shrimp Na, K-ATPase. These data suggest a closer reexamination of the subunit composition of purified Na, K-ATPase preparations. Na, K-ATPase was purified from dog kidney by the method of Jodrgensen. Sodium dodecyl sulfate (SDS)-gel electrophoresis was carried out by the method of Weber and Osborn. When Na, K-ATPase was analyzed by SDS-polyacrylamide gel electrophoresis after boiling in the SDS medium, two closely spaced bands appeared instead of the single α band of the unheated control sample. The two bands were designated as αI (the slower moving band) and αII (the slightly faster band). Molecular weights of αI and αII were determined to be 101,000 and 93,000, respectively. To check the temperature dependence of the band splitting, the enzyme protein solubilized in SDS medium was treated at various temperatures for 10min. Enzyme preparations treated at 50ºC or 60°C gave only the original singlet band, while the doublet structure appeared above 70°C.