Functional expression of N‐terminal truncated α‐subunits of Na,K‐ATPase in Xenopus laevis oocytes

Abstract
N-terminal deletion mutants of Na,K-ATPase α1 isoforms initiating translation at Met34 (α1T1) or at Met43 (α1T2) were expressed in X. laevis oocytes. Compared to β3 cRNA injected controls, the co-expression of α1wt, α1T1, α1T2 with β3 subunits results in a 2- to 3-fold increase of ouabain binding sites, parallelled by a concomitant increase in Na,K-pump current. The apparent K12 for potassium activation of the α1T2/β3 Na,K-pumps is significantly higher than that of the α1wt/β3 or α1T1/β3 Na,K-pumps expressed at the cell surface. Total deletion of the lysine-rich N-terminal domain thus allows the expression of active Na,K-pump but with distinct cation transport properties