Structure of the 5th transmembrane segment of the Na,K-ATPase α subunit: a cysteine-scanning mutagenesis study

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• 作者：Guennoun ; Saï ; da ; Horisberger ; Jean-Daniel
• 关键词：Palytoxin ; Na ; K-ATPase ; Cysteine scanning ; P-type ion-motive ATPase ; Pore structure
• 刊名：FEBS Letters
• 出版年：2000
• 出版时间：September 29, 2000
• 年：2000
• 卷：482
• 期：1-2
• 页码：144-148
• 全文大小：263 K

文摘

To study the structure of the pathway of cations across the Na,K-ATPase, we applied the substituted cysteine accessibility method to the putative 5th transmembrane segment of the α subunit of the Na,K-ATPase of the toad Bufo marinus. Only the most extracellular amino acid position (A⁷⁹⁶) was accessible from the extracellular side in the native Na,K-pump. After treatment with palytoxin, six other positions (Y⁷⁷⁸, L⁷⁸⁰, S⁷⁸², P⁷⁸⁵, E⁷⁸⁶ and L⁷⁹¹), distributed along the whole length of the segment, became readily accessible to a small-size methanethiosulfonate compound (2-aminoethyl methanethiosulfonate). The accessible residues are not located on the same side of an α-helical model but the pattern of reactivity would rather suggest a β-sheet structure for the inner half of the putative transmembrane segment. These results demonstrate the contribution of the 5th transmembrane segment to the palytoxin-induced channel and indicate which amino acid positions are exposed to the pore of this channel.