The gamma subunit modulates Na(+) and K(+) affinity of the renal Na,K-ATPase.
The Na(+),K(+)-ATPase catalyzes the active transport of ions. It has two necessary subunits, alpha and beta, but in kidney it is also associated with a 7.4-kDa protein, the gamma subunit. Stable transfection was used to determine the effect of gamma on Na, K-ATPase properties. When isolated from either kidney or transfected cells, alphabetagamma had lower affinities for both Na(+) and K(+) than alphabeta. A post-translational modification of gamma selectively eliminated the effect on Na(+) affinity, suggesting three configurations (alphabeta, alphabetagamma, and alphabetagamma*) 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 alpha and beta subunit isoforms of Na,K-ATPase. Immunofluorescence was used to detect gamma in rat renal cortex. Cortical ascending limb and some cortical collecting tubules lacked gamma, 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 gamma subunit in renal physiology.
Arystarkhova
E
E
Laboratory of Membrane Biology, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
Wetzel
R K
RK
Asinovski
N K
NK
Sweadner
K J
KJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004285:Dogs; D007668:Kidney / Q000201:enzymology*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013552:Swine; D014162:Transfection
D017931:DNA Primers; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium