title: Characterization of Ca(2+)/H(+) exchange in the plasma membrane of Saccharomyces cerevisiae.
abstract: The characteristics of the Ca(2+)/H(+) exchange were directly investigated in functionally inverted (inside-out) plasma membrane vesicles isolated from yeast using an aqueous two-phase partitioning method. Results showed that following the generation of an inside-acid pH gradient (fluorescence quenching), addition of Ca(2+) caused movement of H(+) out of the vesicles (fluorescence recovery). The Ca(2+)/H(+) exchange displayed saturation kinetics with respect to extravesicular Ca(2+) and ATP concentrations in the plasma membrane, and showed specificity for Ca(2+). The protonophore FCCP (carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone), abolished the fluorescence quenching and consequently inhibited Ca(2+)/H(+) exchange in plasma membrane vesicles. Vanadate, which is known to inhibit the plasma membrane H(+)-ATPase, significantly decreased the Ca(2+)-dependent transport of H(+) out of vesicles. When the electrical potential across the plasma membrane was dissipated with valinomycin and potassium, the rate of Ca(2+)/H(+) exchange increased compared to that of the control without valinomycin, indicating that the stoichiometric ratio for this exchange is greater than 2H(+):Ca(2+). These data suggest that Ca(2+) is transported out of yeast cells through a Ca(2+)/H(+) exchange system that is driven by the proton-motive force generated by the plasma membrane H(+)-ATPase.
authors.affiliation: Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources/College of Agriculture, Hainan University, Haikou, China.
authors.forename: Sha
authors.initials: S
authors.lastname: Hong
authors.forename: Xinli
authors.initials: X
authors.lastname: Cong
authors.forename: Haiyu
authors.initials: H
authors.lastname: Jing
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Xia
authors.forename: Xi
authors.initials: X
authors.lastname: Huang
authors.forename: Xinwen
authors.initials: X
authors.lastname: Hu
authors.forename: Xingyu
authors.initials: X
authors.lastname: Jiang
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D017920:Antiporters / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000502:physiology*; D011522:Protons; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D017920:Antiporters; D027682:Cation Transport Proteins; D011522:Protons; C027614:calcium-hydrogen antiporters; D006859:Hydrogen; D000255:Adenosine Triphosphate; D002118:Calcium
keywords: Ca(2+)/H(+) exchange; H(+)-ATPase; Plasma membrane; Saccharomyces cerevisiae