Cd2+-induced damage to yeast plasma membrane and its alleviation by Zn2+: studies on Schizosaccharomyces pombe cells and reconstituted plasma membrane vesicles |
| |
Authors: | Stephan Aßmann Karel Sigler Milan Höfer |
| |
Institution: | (1) Institute of Botany, University of Bonn, D-53115 Bonn, Germany Fax +49-228-735504, DE;(2) Institute of Microbiology, Czech Academy of Sciences, 14220 Prague 4, Czech Republic, CS |
| |
Abstract: | In Schizosaccharomyces pombe, Cd2+ shares the same uphill uptake system with Zn2+. Both heavy metals inhibited growth, respiration, H+/glucose uptake, and glucose-induced proton extrusion, Cd2+ being a 10–15-fold stronger inhibitor. In contrast, both had a similar effect on the plasma membrane H+-ATPase, enhancing its affinity for ATP and reducing the rate of ATP splitting. Cd2+ caused protracted strong fluidization of the plasma membrane of energized cells, whereas deenergized cells, phosphatidylcholine
liposomes, and plasma membrane fragments, either purified or incorporated into the liposomes, exhibited only a short initial
fluidization. Zn2+, which caused only a marginal membrane fluidization, suppressed the fluidizing action of Cd2+. The fluidizing effect of both heavy metals on liposomes was reduced by the presence of plasma membrane fragments in the
liposome membrane. At 50 μM, Cd2+ brought about loss K+ (18 K+/1 Cd2+) from energized, but not from deenergized cells since Cd2+ must first accumulate in the cells before causing a detectable effect. A simple membrane disruption by external Cd2+ is, therefore, unlikely to be the main mechanism of cadmium-induced potassium loss in intact cells. Zn2+ had virtually no effect below 1 mM concentration, and it again weakened the K+-releasing effect of Cd2+. Cd2+ caused a strong loss of K+ also from K+-containing liposomes, probably because of a direct interaction with liposome phospholipids. Incorporation of plasma membrane
fragments into the liposomes reduced the K+ loss sixfold.
Received: 13 November 1995 / Accepted: 31 January 1996 |
| |
Keywords: | Cadmium uptake Zinc uptake Plasma membrane damage K+ outflow Membrane fluidity Plasma membrane ATPase Schizosaccharomyces pombe |
本文献已被 SpringerLink 等数据库收录! |
|