Functional consequences of substitution of the disulfide-bonded segment, Cys127-Cys150, located in the extracellular domain of the Na,K-ATPase beta subunit: Arg148 is essential for the functional expression of Na,K-ATPase.
The Cys127-Cys150 disulfide-bonded loop (L1) of the Torpedo californica Na,K-ATPase beta 1 subunit was substituted with the corresponding loop of the rat beta 1, mouse beta 2, or pig H,K-ATPase beta subunit. All the substituted mutant beta subunits assembled with the Na,K-ATPase alpha subunit in a trypsin-resistant manner. The mutants with L1 from the Na,K-ATPase beta subunit isoforms (rat beta 1 and mouse beta 2) each formed a functional complex with the Na,K-ATPase alpha subunit. On the other hand, the complex of the alpha subunit with the mutant beta subunit that was substituted with the pig H,K-ATPase beta subunit L1 was inactive as to ATP hydrolysis. Ser131 and Phe148 located within L1 of the pig H,K-ATPase beta subunit-substituted mutant were back-mutated to Pro131 and Arg148, respectively. The Phe148 to Arg mutation restored the ability of the mutant beta subunit substituted with the H,K-ATPase beta subunit L1 to form a functional complex with the alpha subunit. These results suggested that the Cys127-Cys150 loop of the Na,K-ATPase beta 1 subunit, especially Arg148, plays a critical role in the functional expression of Na,K-ATPase.
Ueno
S
S
Department of Pharmacology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu.
Kusaba
M
M
Takeda
K
K
Maeda
M
M
Futai
M
M
Izumi
F
F
Kawamura
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry*; D006868:Hydrolysis; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000201:enzymology; D017434:Protein Structure, Tertiary; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D013552:Swine; D014981:Xenopus
D004220:Disulfides; D001120:Arginine; D000254:Sodium-Potassium-Exchanging ATPase; D003545:Cysteine