The γ Subunit Modulates Na+ and K+Affinity of the Renal Na,K-ATPase

• Published in: The Journal of biological chemistry Vol. 274; no. 47; pp. 33183 - 33185
• Main Authors: Arystarkhova, Elena, Wetzel, Randall K., Asinovski, Natalya K., Sweadner, Kathleen J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.11.1999
• Subjects: Amino Acid Sequence; Animals; Base Sequence; DNA Primers; Dogs; Kidney - enzymology; Potassium - metabolism; Rats; Sodium - metabolism; Sodium-Potassium-Exchanging ATPase - chemistry; Sodium-Potassium-Exchanging ATPase - genetics; Sodium-Potassium-Exchanging ATPase - metabolism; Swine; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.47.33183

The Na+,K+-ATPase catalyzes the active transport of ions. It has two necessary subunits, α and β, but in kidney it is also associated with a 7.4-kDa protein, the γ subunit. Stable transfection was used to determine the effect of γ on Na,K-ATPase properties. When isolated from either kidney or transfected cells, αβγ had lower affinities for both Na+ and K+ than αβ. A post-translational modification of γ selectively eliminated the effect on Na+ affinity, suggesting three configurations (αβ, αβγ, and αβγ*) conferring different stable properties to Na,K-ATPase. In the nephron, segment-specific differences in Na+ affinity have been reported that cannot be explained by the known α and β subunit isoforms of Na,K-ATPase. Immunofluorescence was used to detect γ in rat renal cortex. Cortical ascending limb and some cortical collecting tubules lacked γ, correlating with higher Na+ affinities in those segments reported in the literature. Selective expression in different segments of the nephron is consistent with a modulatory role for the γ subunit in renal physiology.