Evidence for a zinc/proton antiporter in rat brain.
The data presented in this paper are consistent with the existence of a plasma membrane zinc/proton antiport activity in rat brain. Experiments were performed using purified plasma membrane vesicles isolated from whole rat brain. Incubating vesicles in the presence of various concentrations of 65Zn2+ resulted in a rapid accumulation of 65Zn2+. Hill plot analysis demonstrated a lack of cooperativity in zinc activation of 65Zn2+ uptake. Zinc uptake was inhibited in the presence of 1 mM Ni2+, Cd2+, or CO2+. Calcium (1 mM) was less effective at inhibiting 65Zn2+ uptake and Mg2+ and Mn2+ had no effect. The initial rate of vesicular 65Zn2+ uptake was inhibited by increasing extravesicular H+ concentration. Vesicles preloaded with 65Zn2+ could be induced to release 65Zn2+ by increasing extravesicular H+ or addition of 1 mM nonradioactive Zn2+. Hill plot analysis showed a lack of cooperativity in H+ activation of 65Zn2+ release. Based on the Hill analyses, the stoichiometry of transport may include Zn2+/Zn2+ exchange and Zn2+/H+ antiport, the latter being potentially electrogenic. Zinc/proton antiport may be an important mode of zinc uptake into neurons and contribute to the reuptake of zinc to replenish presynaptic vesicle stores after stimulation.
Colvin
R A
RA
Department of Biological Sciences, Ohio University, Athens 45701, USA. rcolvin1@ohiou.edu
Davis
N
N
Nipper
R W
RW
Carter
P A
PA
D000818:Animals; D017920:Antiporters / Q000378:metabolism*; D001692:Biological Transport; D001921:Brain / Q000378:metabolism*; D002412:Cations; D002462:Cell Membrane / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D051381:Rats; D015032:Zinc / Q000378:metabolism*
D017920:Antiporters; D002412:Cations; D006859:Hydrogen; D015032:Zinc