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J Bacteriol, February 1998, p. 483-490, Vol. 180, No. 3
School of Biochemistry and Molecular Genetics
and Cooperative Research Centre (CRC) for Food Industry Innovation,
University of New South Wales, Sydney NSW 2052, Australia
Received 20 August 1997/Accepted 25 November 1997
Linoleic acid hydroperoxide (LoaOOH) formed during free radical
attack on long-chain unsaturated fatty acids is an important source of
biomembrane damage and is implicated in the onset of atherosclerosis,
hepatic diseases, and food rancidity. LoaOOH is toxic to wild-type
Saccharomyces cerevisiae at a very low concentration (0.2 mM) relative to other peroxides. By using isogenic mutant strains, the
possible roles of glutathione (gsh1 and gsh2),
glutathione reductase (glr1), respiratory competence
([rho0] petite), and yAP-1p-mediated
expression (yap1) in conferring LoaOOH resistance have been
examined. Respiration-related processes were essential for maximal
toxicity and adaptation, as evidenced by the fact that the
[rho0] petite mutant was most resistant to
LoaOOH but could not adapt. Furthermore, when respiration was blocked
by using inhibitors of respiration and mutants defective in
respiratory-chain components, cells became more resistant. An important
role for reduced glutathione and yAP-1 in the cellular response to
LoaOOH was shown, since the yap1 and glr1
mutants were more sensitive than the wild type. In addition, total
glutathione peroxidase activity increased following treatment with
LoaOOH, indicating a possible detoxification role for this enzyme.
Yeast also showed an adaptive response when pretreated with a nonlethal
dose of LoaOOH (0.05 mM) and subsequently treated with a lethal dose
(0.2 mM), and de novo protein synthesis was required, since adaptation
was abolished upon treatment of cells with cycloheximide (25 µg
ml
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Toxicity of Linoleic Acid Hydroperoxide to
Saccharomyces cerevisiae: Involvement of a
Respiration-Related Process for Maximal Sensitivity and
Adaptive Response
1). The wild-type adaptive response to LoaOOH was
independent of those for the superoxide-generating agents paraquat and
menadione and also of those for the organic hydroperoxides cumene
hydroperoxide and tert-butyl hydroperoxide. Pretreatment
with LoaOOH induced resistance to hydrogen peroxide, while pretreatment
of cells with malondialdehyde (a lipid peroxidation product) and heat
shock (37°C) gave cross-adaptation to LoaOOH, indicating that yeast has effective overlapping defense systems that can detoxify fatty acid
hydroperoxides directly or indirectly.
*
Corresponding author. Mailing address: School of
Biochemistry and Molecular Genetics and Cooperative Research Centre
(CRC) for Food Industry Innovation, University of New South Wales,
Sydney NSW 2052, Australia. Phone: 61 (2) 9385 2089. Fax: 61 (2) 9385 1050. E-mail: i.dawes{at}unsw.edu.au.
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