Abstract
(Na, K) ATPase is composed of two heterologus subunits; a catalytic α subunit and a glycosy lated β subunit whose role remains unclear. To elucidate a possible role of the β subunit, the α and β subunits of Torpedo californica (Na, K) ATPase were expressed in the Xenopus oocytes system which allows the specific programmed synthesis of different subunits in a cell by alternately injecting individual mRNA. When oocytes were injected with mRNA α alone, no significant increase in (Na, K) ATPase activity was observed, whereas a slight increase was detected in oocytes injected with mRNA β alone. The pre-existing β subunit, which had been synthesized by injecting mRNA β, could assemble with the α subunit, expressed later in the single oocytes and the resulting α β acquired both ouabain-binding and (Na, K) ATPase activities. The results reported in this paper strongly indicate that the β subunit plays an essential role, at least in the biogenesis of the enzyme.
