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

AUTOR(ES)

Eakle, K A

RESUMO

Recently, a beta subunit for the rat gastric H+,K(+)-ATPase (HK beta), which is structurally similar to the beta subunit of Na+, K(+)-ATPase, has been cloned and characterized. Using heterologous expression in yeast, we have tested the specificity of beta subunit assembly with different isoforms of the alpha subunit of Na+, K(+)-ATPase. Coexpression in yeast cells of the HK beta with both the sheep alpha 1 subunit and the rat alpha 3 subunit isoforms of Na+, K(+)-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 (Kd, 5-10 nM) and are expressed at levels similar to those formed with the rat beta 1 subunit of Na+, K(+)-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+ for ouabain binding. These data suggest that the structure of the beta subunit may play a role in sodium pump function.

Documentos Relacionados

• Structural organization and transcription of the mouse gastric H+, K(+)-ATPase beta subunit gene.
• Activation of the Na+, K(+)-ATPase in Narcine brasiliensis.
• High-affinity ouabain binding by a chimeric gastric H+,K+-ATPase containing transmembrane hairpins M3-M4 and M5-M6 of the α1-subunit of rat Na+,K+-ATPase
• Amino acid substitutions in the rat Na+, K(+)-ATPase alpha 2-subunit alter the cation regulation of pump current expressed in HeLa cells.
• Oxygen consumption for K+ uptake during post-stimulatory activation of Na+, K(+)-ATPase in perfused rat mandibular gland.