High-affinity ouabain binding by yeast cells expressing Na super(+),K super(+)-ATPase alpha subunits and the gastric H super(+),K super(+)-ATPase beta subunit

• Published in: Proceedings of the National Academy of Sciences - PNAS 1992-01, Vol.89 (7), p.2834-2838
• Main Authors: Eakle, KA, Kim, Kyu Seong, Kabalin, MA, Farley, R A
• Format: Article
• Language: English
• Subjects: H super(+)/K super(+)-transporting ATPase; ouabain; Saccharomyces cerevisiae
• ISSN: 0027-8424

Recently, a beta subunit for the rat gastric H super(+),K super(+)-ATPase (HK beta ), which is structurally similar to the beta subunit of Na super(+),K super(+)-ATPase, has been cloned and characterized. We have tested the specificity of beta subunit assembly with different isoforms of the alpha subunit of Na super(+),K super(+)-ATPase. Coexpression in yeast cells of the HK beta with both the sheep alpha 1 subunit and the rat alpha 2 subunit isoforms of Na super(+),K super(+)-ATPase ( alpha 1 and alpha 3, respectively) leads to the appearance of high-affinity ouabain-binding sites in yeast membranes. These ouabain-binding sites ( alpha 1 plus HK beta , alpha 3 plus HK beta ) have a high affinity for ouabain (K sub(d), 5-10 nM) and are expressed at levels similar to those formed with the rat beta 1 subunit of Na super(+),K super(+)-ATPase ( beta 1) ( alpha 1 plus beta 1 or alpha 3 plus beta 1). Potassium acts as a specific antagonist of ouabain binding by alpha 1 plus HK beta and alpha 3 plus HK beta just like sodium pumps formed with beta 1. Sodium pumps formed with the HK beta , however, show quantitative differences in their affinity for ouabain and in the antagonism of K super(+) for ouabain binding.