This review summarizes our experiments on the significance of the β-subunit in the functional expression of Na+/K+-ATPase. The β-subunit acts like a receptor for the α-subunit in the biogenesis of Na+/K+-ATPase and facilitates the correct folding of the α-subunit in the membrane. The α-subunit synthesized in the absence of the β-subunit is subjected to rapid degradation in the endoplasmic reticulum. Several assembly sites are assigned in the sequence of the β-subunit from the cytoplasmic NH2-terminal domain to the extracellular COOH-terminus: the NH2-terminal region of the extracellular domain, the conservative proline in the third disulfide loop, the hydrophobic amino acid residues near the COOH-terminus and the cysteine residues forming the second and the third disulfide bridges. Upon assembly, the β-subunit confers a resistance to trypsin on the α-subunit. The conformations induced in the α-subunit of Na+/K+-ATPase by Na+/K+- and H+/K+-ATPase β-subunits are somehow different from each other and are named the NK-type and KH-type, respectively. The extracellular domain of the β-subunit is involved in the folding of the α-subunit leading to trypsin-resistant conformations. The sequences from Cys150 to the COOH-terminus of the Na+/K+-ATPase β-subunit and from Ile89 to the COOH–terminus of the H+/K+-ATPase β-subunit are necessary to form trypsin-resistant conformations of the NK- and HK-type. respectively. The first disulfide loop of the extracellular domain of the β-subunits is critical in the expression of functional Na+/K+-ATPase.
Review Article| April 01 1997
Significance of the β-Subunit in the Biogenesis of Na+/K+-ATPase
1Department of Biology, University of Occupational and Environmental Health, School of Medicine, Kitakyushu 807, Japan.
2Department of Pharmacology, University of Occupational and Environmental Health, School of Medicine, Kitakyushu 807, Japan.
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Biosci Rep (1997) 17 (2): 173–188.
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Susumu Ueno, Kazuo Takeda, Shunsuke Noguchi, Masaru Kawamura; Significance of the β-Subunit in the Biogenesis of Na+/K+-ATPase. Biosci Rep 1 April 1997; 17 (2): 173–188. doi: https://doi.org/10.1023/A:1027333529412
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