ISSN:
1572-8773
Keywords:
cadmium resistance
;
cadmium toxicity
;
energetic processes
;
primary targets
;
secondary effects
;
Staphylococcus aureus
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract In washed cells of cadmium-sensitive Staphylococcus aureus 17810S oxidizing glutamate, initial Cd2+++ influx via the Mn2+ porter down membrane potential (Δψ) was fast due to involvement of energy generated by two proton pumps—the respiratory chain and the ATP synthetase complex working in the hydrolytic direction. Such an unusual energy drain for rapid initial Cd2+ influx is suggested to be due to a series of toxic events elicited by Cd2+ accumulation down Δψ generated via the redox proton pump: (i) strong inhibition of glutamate oxidation accompanied by a decrease of electrochemical proton gradient (Δμ H +) formation via the respiratory chain, (ii) automatic reversal of ATP synthetase from biosynthetic to hydrolytic mode, which was monitored by a decrease of Δμ H +-dependent ATP synthesis, (iii) acceleration of the initial Cd2+ influx down Δψ generated the reversed ATP synthetase, the alternative proton pump hydrolyzing endogenous ATP. The primary, cadmium-sensitive targets in strain 17810S seem to be dithiols located in the cytoplasmic glutamate oxidizing system, prior to the membrane-embedded NADH oxidation system. Inhibition by Cd2+ of Δμ H +-dependent ATP synthesis and of pH gradient (ΔpH)-linked [14C]glutamate transport is a secondary effect due to cadmium-mediated inhibition of Δμ H + generation at the cytoplasmic level. In washed cells of cadmium-resistant S. aureus 17810R oxidizing glutamate, Cd2+ accumulation was prevented due to activity of the plasmid-coded Cd2+ efflux system. Consequently, Δμ H +-producing and -requiring processes were not affected by Cd2+.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00143376
