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: Glu63, His72/His73, and Asp78. These amino acids are highly conserved among H+-sensitive ASICs and are candidates for the “H+ sensor” of ASICs.
Journal of Biological Chemistry
American Society for Biochemistry and Molecular Biology
Digital Object Identifier (DOI)
Paukert M, Chen X, Polleichtner G, Schindelin H, Grunder S. Candidate amino acids involved in H+ gating of acid-sensing ion channel 1a. The Journal of biological chemistry. 2008;283(1):572-81. doi: 10.1074/jbc.M706811200. PubMed PMID: 17981796.
© 2008 by The American Society for Biochemistry and Molecular Biology, Inc