Abstract
BackgroundReactive carbonyl species (RCS), such as methylglyoxal (MG) and glyoxal (GO), are synthesized as toxic metabolites in living systems. Mechanisms of RCS detoxification include the glutathione (GSH)-dependent system consisting of glyoxalase I (GLO1) and glyoxalase II (GLO2), and GSH-independent system involving glyoxalase III (GLO3). Hsp31 and DJ-1 proteins are weakly homologous to each other and belong to two different subfamilies of the DJ-1/Hsp31/PfpI superfamily. Recently, the Escherichia coli Hsp31 protein and the DJ-1 proteins from Arabidopsis thaliana and metazoans have been demonstrated to have GLO3 activity.ResultsWe performed a systematic survey of homologs of DJ-1 and Hsp31 in fungi. We found that DJ-1 proteins have a very limited distribution in fungi, whereas Hsp31 proteins are widely distributed among different fungal groups. Phylogenetic analysis revealed that fungal and metazoan DJ-1 proteins and bacterial YajL proteins are most closely related and together form a sister clade to bacterial and fungal Hsp31 proteins. We showed that two Schizosaccharomyces pombe Hsp31 proteins (Hsp3101 and Hsp3102) and one Saccharomyces cerevisiae Hsp31 protein (ScHsp31) displayed significantly higher in vitro GLO3 activity than S. pombe DJ-1 (SpDJ-1). Overexpression of hsp3101, hsp3102 and ScHSP31 could confer MG and GO resistance on either wild-type S. pombe cells or GLO1 deletion of S. pombe. S. pombe DJ-1 and Hsp31 proteins exhibit different patterns of subcellular localization.ConclusionsOur results suggest that fungal Hsp31 proteins are the major GLO3 that may have some role in protecting cells from RCS toxicity in fungi. Our results also support the view that the GLO3 activity of Hsp31 proteins may have evolved independently from that of DJ-1 proteins.
Highlights
Reactive carbonyl species (RCS), such as methylglyoxal (MG) and glyoxal (GO), are synthesized as toxic metabolites in living systems
To determine the subcellular localization of Hsp3103 and to verify the results from the genome-wide study, we examined the localization of the C-terminal green fluorescent protein (GFP) fusions of S. pombe DJ-1 (SpDJ-1) and Hsp3101-3105 expressed from their endogenous loci
We found that overexpression of ScHSP31 and E. coli Hsp31 (EcHsp31) could increase the resistance of S. pombe cells to MG and GO, suggesting functional conservation of Hsp31 proteins from E. coli, S. cerevisiae and S. pombe
Summary
Reactive carbonyl species (RCS), such as methylglyoxal (MG) and glyoxal (GO), are synthesized as toxic metabolites in living systems. Mechanisms of RCS detoxification include the glutathione (GSH)-dependent system consisting of glyoxalase I (GLO1) and glyoxalase II (GLO2), and GSH-independent system involving glyoxalase III (GLO3). Hsp and DJ-1 proteins are weakly homologous to each other and belong to two different subfamilies of the DJ-1/Hsp31/PfpI superfamily. Reactive carbonyl species (RCS) are usually produced as metabolites in living systems including prokaryotes, fungi, plants, and animals. Among RCS are the highly reactive α-carbonyl compounds methylglyoxal (MG) and glyoxal (GO). GO is generated by oxidative degradation of lipid and DNA, and oxidation of glycolaldehyde. RCS can rapidly react with the amino groups in proteins, nucleic acids and lipids to form toxic or mutagenic advanced glycation endproducts (AGE) and cause carbonyl stress.
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