Mutation of a conserved proline residue in the beta-subunit ectodomain prevents Na(+)-K(+)-ATPase oligomerization.
A highly conserved sequence motif (4 tyrosines and 1 proline: YYPYY) of the Na(+)-K(+)-adenosinetriphosphatase (ATPase) beta 1-subunit ectodomain has been mutagenized to study its possible role in alpha/beta-assembly and sodium pump function. Single as well as double tyrosine mutants (tyrosine to phenylalanine: Y to F) of Xenopus laevis beta 1-subunits are able to associate with alpha 1-subunits and form functional Na-K pumps at the plasma membrane that are indistinguishable from wild-type alpha 1, beta 1-Na-K pumps (as assessed by measurements of ouabain binding, 86Rb flux, Na-K pump current, and activation by external potassium). In contrast, a single proline mutation (proline to glycine: P244G) reduced by > 90% the proper assembly and function of Na(+)-K(+)-ATPase, despite a normal rate of synthesis and core glycosylation. Our data indicate that proline-244 plays a critical role in the proper folding of the beta-subunit and its ability to associate efficiently with the alpha 1-subunit in the endoplasmic reticulum.
Geering
K
K
Institut de Pharmacologie et de Toxicologie de l'Université, Lausanne, Switzerland.
Jaunin
P
P
Jaisser
F
F
Mérillat
A M
AM
Horisberger
J D
JD
Mathews
P M
PM
Lemas
V
V
Fambrough
D M
DM
Rossier
B C
BC
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics*; D011392:Proline / Q000235:genetics*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis
D010446:Peptide Fragments; D011392:Proline; D000254:Sodium-Potassium-Exchanging ATPase