Molecular weights of alpha beta-protomeric and oligomeric units of soluble (Na+, K+)-ATPase determined by low-angle laser light scattering after high-performance gel chromatography.

The (Na+, K+)-ATPase of canine renal outer medulla was solubilized with a nonionic surfactant, octaethylene glycol n-dodecyl ether (C12E8), in the presence of 0.2 M sodium ion. The solubilized ATPase retained 74% of the enzymatic activity expressed before solubilization. Molecular species of the solubilized ATPase were analyzed by high-performance chromatography through a TSK-GEL G3000SW column in the presence of 1 mg/ml C12E8 at 23 degrees C. The eluate was monitored by one or two monitors chosen from the following: an ultraviolet absorption monitor, a precision differential refractometer and a low-angle laser light scattering photometer. The three kinds of elution pattern thus obtained can best be interpreted by assuming the presence of at least four kinds of protein component with molecular weights 1 740 000 +/- 230 000, 836 000 +/- 82 000, 286 000 +/- 30 000 and 123 000 +/- 8 000, respectively. Among them, those with the last two molecular weight were the major components. The amounts of the first three components were found to increase with time during the incubation before application to the column at the expense of that of the last one. The amounts of the last two were 18 and 73%, respectively, when measured immediately after the solubilization. A stoichiometric composition of 1:1 molar ratio for the alpha and beta polypeptide chains was obtained for the two major components as well as for the intact ATPase by high-performance gel chromatography in the presence of sodium dodecyl sulfate using the same column as above. The (Na+, K+)-ATPase was, thus, indicated to be solubilized with C12E8 to give the alpha beta-protomer and its dimer as the main components.