title: NCX1: mechanism of transport.
abstract: The plasma membrane Na(+)/Ca(2+) exchanger (NCX) plays a critical role in the maintenance of Ca(2+) homeostasis in a variety of tissues. NCX accomplishes this task by either lowering or increasing the intracellular Ca(2+) concentration, a process which depends on electrochemical gradients. During each cycle, three Na(+) are transported in the opposite direction to one Ca(2+), resulting in an electrogenic transport that can be measured as an ionic current.The residues involved in ion translocation are unknown. A residue thought to be important for Na(+) and/or Ca(2+) transport, Ser(110), was replaced with a cysteine, and the properties of the resulting exchanger mutant were analyzed using the giant patch technique. Data indicate that this residue, located in transmembrane segment 2 (part of the α-1 repeat), is important for both Na(+) and Ca(2+) translocations. Using cysteine susceptibility analysis, we demonstrated that Ser(110) is exposed to the cytoplasm when the exchanger is in the inward state configuration.
authors.affiliation: Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095-1760, USA. ottolia@mednet.ucla.edu
authors.forename: Michela
authors.initials: M
authors.lastname: Ottolia
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Philipson
mesh_terms: D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D017136:Ion Transport / Q000502:physiology; D009154:Mutation; D017433:Protein Structure, Secondary; D012964:Sodium / Q000737:chemistry / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D019831:Sodium-Calcium Exchanger; C110374:sodium-calcium exchanger 1; D012964:Sodium; D002118:Calcium