Coexpression of alpha 1 with putative beta 3 subunits results in functional Na+/K+ pumps in Xenopus oocytes.
The active Na+/K+ pump is composed of an alpha and a beta subunit. Until now, three putative isoforms of the beta subunit have been identified that share sequence similarity. We have expressed the beta 1 and beta 3 isoforms of Xenopus laevis Na+/K(+)-ATPase in Xenopus oocytes to compare functional properties of the Na+/K+ pump, including either of these two isoforms. Na+/K+ pump current, estimated as K(+)-induced outward current in voltage-clamped oocytes, was doubled by coexpression of alpha 1 subunits with either isoform of the beta subunit compared to expression of alpha 1 subunits alone. The kinetics of activation by external K+ and the voltage dependence of the electrogenic activity of the Na+/K+ pump were similar with both beta isoforms, indicating that both beta 1 and beta 3 isoforms can support expression at the oocyte surface of an active Na+/K+ pump with similar functional properties.
Horisberger
J D
JD
Institut of Pharmacology and Toxicology, University of Lausanne, Switzerland.
Jaunin
P
P
Good
P J
PJ
Rossier
B C
BC
Geering
K
K
D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000201:enzymology; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007473:Ion Channels / Q000737:chemistry* / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials; D009865:Oocytes; D011188:Potassium / Q000494:pharmacology; D011994:Recombinant Proteins; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000502:physiology; D013327:Strophanthidin / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
D007473:Ion Channels; D011994:Recombinant Proteins; D013327:Strophanthidin; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium