期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 283, 期 1, 页码 572-581出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M706811200
关键词
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Acid-sensing ion channels are ligand-gated cation channels, gated by extracellular H+. H+ is the simplest ligand possible, and whereas for larger ligands that gate ion channels complex binding sites in the three-dimensional structure of the proteins have to be assumed, H+ could in principle gate a channel by titration of a single amino acid. Experimental evidence suggests a more complex situation, however. For example, it has been shown that extracellular Ca2+ ions compete with H+; probably Ca2+ ions bound to the extracellular loop of ASICs stabilize the closed state of the channel and have to be displaced before the channel can open. In such a scheme, amino acids contributing to Ca2+ binding would also be candidates contributing to H+ gating. In this study we systematically screened more than 40 conserved, charged amino acids in the extracellular region of ASIC1a for a possible contribution to H+ gating. We identified four amino acids where substitution strongly affects H+ gating: Glu(63), His(72)/His(73), and Asp(78). These amino acids are highly conserved among H+-sensitive ASICs and are candidates for the H+ sensor of ASICs.
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