Apr 5, 1976

Kinetics of ion translocation across charged membranes mediated by a two-site transport mechanism. Effects of polyvalent cations upon rubidium uptake into yeast cells

Biochimica Et Biophysica Acta
A P Theuvenet, G W Borst-Pauwels

Abstract

(1) The effect of surface charge upon the kinetics of monovalent cation translocation via a two-site mechanism is investigated theroretically. (2) According to the model dealt with, typical relations are expected for the dependence of the kinetic parameters of the translocation process upon the concentration of a polyvalent cation, differing essentially from those derived for the case in which the membrane carries no excess charge. (3) Even when a polyvalent cation does not compete with the substrate cation for binding to the translocation sites, apparently competitive inhibition may occur when the membrane is negatively charged. (4) The model is tested experimentally by studying the effects of the polyvalent cations Mg2+, Sr2+, Ca2+, Ba2+ and Al3+ upon Rb+ uptake into yeast cells at pH 4.5 A good applicability is found. (5) Equimolar concentrations of polyvalent cations reduce the rate of the Rb+ uptake into yeast cells in the order Mg2+ less than Sr2+ less than Ca2+ less than Ba2+ less than Al3+. (6) The conclusion is reached that the reduction in the rate of Rb+ uptake caused by the polyvalent cations applied results mainly from screening of the negative fixed charges on the membrane surface and binding to these negative sit...Continue Reading

  • References3
  • Citations19

References

Mentioned in this Paper

Tissue Membrane
Structure-Activity Relationship
Uptake
Etiology
Rubidium
Cations
Intracellular Translocation
Cations, Monovalent
Aluminum
Saccharomyces cerevisiae

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