RipAY, a Plant Pathogen Effector Protein, Exhibits Robust γ-Glutamyl Cyclotransferase Activity When Stimulated by Eukaryotic Thioredoxins

The plant pathogenic bacterium Ralstonia solanacearum injects more than 70 effector proteins (virulence factors) into the host plant cells via the needle-like structure of a type III secretion system. The type III secretion system effector proteins manipulate host regulatory networks to suppress def...

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Bibliographic Details
Published in:The Journal of biological chemistry 2016-03, Vol.291 (13), p.6813-6830
Main Authors: Fujiwara, Shoko, Kawazoe, Tomoki, Ohnishi, Kouhei, Kitagawa, Takao, Popa, Crina, Valls, Marc, Genin, Stéphane, Nakamura, Kazuyuki, Kuramitsu, Yasuhiro, Tanaka, Naotaka, Tabuchi, Mitsuaki
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Bacterial Proteins - chemistry
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Botany
Botànica
Escherichia coli - genetics
Escherichia coli - metabolism
gamma-Glutamylcyclotransferase - chemistry
gamma-Glutamylcyclotransferase - genetics
gamma-Glutamylcyclotransferase - metabolism
Gene Expression Regulation, Bacterial
Gene Regulatory Networks
Glutathione - metabolism
Host-Pathogen Interactions
Membrane Proteins - genetics
Membrane Proteins - metabolism
Microbiology
Molecular Sequence Data
Oxidation-Reduction
Oxidation-reduction reaction
Peroxiredoxins - genetics
Peroxiredoxins - metabolism
Phylogeny
plant defense
Plants - microbiology
Protein Structure, Tertiary
Proteins
Proteïnes
Ralstonia solanacearum - classification
Ralstonia solanacearum - enzymology
Ralstonia solanacearum - genetics
Ralstonia solanacearum - pathogenicity
Reacció d'oxidació-reducció
Recombinant Proteins - chemistry
Recombinant Proteins - genetics
Recombinant Proteins - metabolism
redox regulation
Saccharomyces cerevisiae
Saccharomyces cerevisiae - genetics
Saccharomyces cerevisiae - metabolism
Saccharomyces cerevisiae Proteins - genetics
Saccharomyces cerevisiae Proteins - metabolism
Sequence Alignment
Structural Homology, Protein
thioredoxin
Thioredoxins - genetics
Thioredoxins - metabolism
type III secretion system (T3SS)
Type III Secretion Systems - genetics
Type III Secretion Systems - metabolism
Virulence Factors - chemistry
Virulence Factors - genetics
Virulence Factors - metabolism
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Summary:The plant pathogenic bacterium Ralstonia solanacearum injects more than 70 effector proteins (virulence factors) into the host plant cells via the needle-like structure of a type III secretion system. The type III secretion system effector proteins manipulate host regulatory networks to suppress defense responses with diverse molecular activities. Uncovering the molecular function of these effectors is essential for a mechanistic understanding of R. solanacearum pathogenicity. However, few of the effectors from R. solanacearum have been functionally characterized, and their plant targets remain largely unknown. Here, we show that the ChaC domain-containing effector RipAY/RSp1022 from R. solanacearum exhibits γ-glutamyl cyclotransferase (GGCT) activity to degrade the major intracellular redox buffer, glutathione. Heterologous expression of RipAY, but not other ChaC family proteins conserved in various organisms, caused growth inhibition of yeast Saccharomyces cerevisiae, and the intracellular glutathione level was decreased to ∼30% of the normal level following expression of RipAY in yeast. Although active site mutants of GGCT activity were non-toxic, the addition of glutathione did not reverse the toxicity, suggesting that the toxicity might be a consequence of activity against other γ-glutamyl compounds. Intriguingly, RipAY protein purified from a bacterial expression system did not exhibit any GGCT activity, whereas it exhibited robust GGCT activity upon its interaction with eukaryotic thioredoxins, which are important for intracellular redox homeostasis during bacterial infection in plants. Our results suggest that RipAY has evolved to sense the host intracellular redox environment, which triggers its enzymatic activity to create a favorable environment for R. solanacearum infection.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M115.678953