title: Functional analysis of amino acids of the Na+/H+ exchanger that are important for proton translocation.
abstract: The Na+/H+ exchanger is an integral membrane protein found in the plasma membrane of eukaryotic and prokaryotic cells. In eukaryotes it functions to exchange one proton for a sodium ion. In mammals it removes intracellular protons while in plants and fungal cells the plasma membrane form removes intracellular sodium in exchange for extracellular protons. In this study we used the Na+/H+ exchanger of Schizosaccharomyces pombe (Sod2) as a model system to study amino acids critical for activity of the protein. Twelve mutant forms of the Na+/H+ exchanger were examined for their ability to translocate protons as assessed by a Cytosensor microphysiometer. Mutation of the amino acid Histidine 367 resulted in defective proton translocation. The acidic residues Asp145, Asp178, Asp266 and Asp267 were important in the proton translocation activity of the Na+/H+ exchanger. Mutation of amino acids His98, His233 and Asp241 did not significantly impair proton translocation by the Na+/H+ exchanger. These results confirm that polar amino acids are important in proton flux activity of Na+/H+ exchangers.
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Wiebe
authors.forename: Carmen
authors.initials: C
authors.lastname: Rieder
authors.forename: Paul G
authors.initials: PG
authors.lastname: Young
authors.forename: Pavel
authors.initials: P
authors.lastname: Dibrov
authors.forename: Larry
authors.initials: L
authors.lastname: Fliegel
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001224:Aspartic Acid / Q000737:chemistry; D001692:Biological Transport; D002412:Cations; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D007477:Ions; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011522:Protons; D012568:Schizosaccharomyces / Q000378:metabolism; D012964:Sodium / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry*; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors; D000099156:Superoxide Dismutase 2
chemical_list: D000596:Amino Acids; D001224:Aspartic Acid; D002412:Cations; D004247:DNA; D006639:Histidine; D007477:Ions; D011522:Protons; D012964:Sodium; D012965:Sodium Chloride; D017923:Sodium-Hydrogen Exchangers; D013482:Superoxide Dismutase; D000099156:Superoxide Dismutase 2