title: Toxin binding reveals two open state structures for one acid-sensing ion channel.
abstract: Of the three principal conformations of acid-sensing ion channels (ASICs)--closed, open and desensitized--only the atomic structure of the desensitized conformation had been known. Two recent papers report the crystal structure of chicken ASIC1 in complex with the spider toxin psalmotoxin 1, and one of these studies finds that, depending on the pH, channels are in two different open conformations. Compared with the desensitized conformation, toxin binding induces only subtle structural changes in the lower part of the large extracellular domain but a complete rearrangement of the two transmembrane domains (TMDs), suggesting that desensitization gating (the transition from open to desensitized) is mainly associated with conformational rearrangements of the TMDs. Moreover, the study reveals how two different arrangements of the TMDs in the open state give rise to ion pores with different selectivity for monovalent cations.
authors.affiliation: Institute of Physiology, RWTH Aachen University, Aachen, Germany. sgruender@ukaachen.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Gründer
authors.forename: Katrin
authors.initials: K
authors.lastname: Augustinowski
mesh_terms: D062565:Acid Sensing Ion Channels / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D002645:Chickens; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013111:Spider Venoms / Q000737:chemistry / Q000378:metabolism*
chemical_list: D062565:Acid Sensing Ion Channels; C413209:PcTX1 protein, Psalmopoeus cambridgei; D010455:Peptides; D013111:Spider Venoms