Expression of active alpha-3 subunit of rat brain Na+,K+-ATPase from the messenger RNA injected into Xenopus oocytes.

Abstract Cloned cDNA encoding the so-far uncharacterized alpha-3 subunit of rat brain Na + ,K + -ATPase (Hara et al. (1987) J. Biochem. 102, 43–58, Shull et al. (1986) Biochemistry 25, 8125–8132) was incorporated into a vector carrying the SP6 promoter. The mRNA produced in vitro was injected into Xenopus oocytes with the mRNA encoding the Na + ,K + -ATPase beta subunit of Torpedo electroplax. Increased Na + ,K + -ATPase activity in the oocyte membrane was observed. This newly expressed activity was inhibited by ouabain (Ki=1.5×10 −7 M), suggesting that the alpha-3 subunit of rat brain Na + ,K + -ATPase is a highly ouabain-sensitive catalytic subunit.