Membrane Topology of the α Subunit of Na,K-ATPase
Although the amino acid sequence of the Na,K-ATPase is known, the transmembrane folding of its a subunit is the subject of considerable controversy. Several lines of evidence (8) support hydropathy plots that predict 4 transmembrane spans in the Nterminal third of the sequence. There is also general agreement that the middle third of the polypeptide chain is entirely cytoplasmic. The confusion lies in the C-terminal third of the sequence where hydropathy plots are ambiguous and models with three, four or six spans have been proposed. Rigorous identification of sites exposed on one side of the membrane or the other is essential for the development of a reliable folding model.
KeywordsGold Particle Colloidal Gold Immunoelectron Microscopy Cytoplasmic Side Cyanogen Bromide
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