PMID:9663682

Citation	Wilson, TJ, Bertrand, N, Tang, JL, Feng, JX, Pan, MQ, Barber, CE, Dow, JM and Daniels, MJ (1998) The rpfA gene of Xanthomonas campestris pathovar campestris, which is involved in the regulation of pathogenicity factor production, encodes an aconitase. Mol. Microbiol. 28:961-70
Abstract	Xanthomonas campestris pv campestris (Xcc) is a plant pathogenic bacterium that controls the production of pathogenicity factors in part by a cluster of genes designated rpf (regulation of pathogenicity factors). Sequence analysis of one of these genes (rpfA) revealed an open reading frame with amino acid sequence similarity to aconitases from other bacteria. Aconitase activity was lower in cellular extracts of an rpfA::Tn5 mutant than in those from the wild type. A zymogram of aconitase activity after native gel electrophoresis showed the presence of two distinct aconitases in Xcc; the major aconitase was absent in the rpfA::Tn5 mutant. This mutant also had reduced levels of extracellular enzymes and extracellular polysaccharide (EPS). Supplying rpfA in trans to the rpfA::Tn5 mutant restored both the major aconitase activity and the synthesis of these pathogenicity factors. The transcription of the genes for two extracellular enzymes (prtA, encoding a serine protease, and engXCA, encoding endoglucanase) was reduced in the rpfA mutant background. Because some eukaryotic aconitases are also involved in iron regulation, we explored a possible connection between rpfA and iron metabolism. Intracellular iron levels in the mutants were lower than in the wild type as assessed by sensitivity to the iron-activated antibiotic, streptonigrin. Wild-type bacteria grown in iron-deficient conditions had a similar sensitivity to streptonigrin as the aconitase mutant. Overall, these results suggest that a prokaryotic aconitase can also act as a regulator of gene expression and that the regulation is possibly related to changes in intracellular iron levels.
Links	PubMed
Keywords	Aconitate Hydratase/genetics; Aconitate Hydratase/metabolism; Amino Acid Sequence; Animals; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Base Sequence; DNA, Bacterial; Drug Resistance, Microbial; Genes, Bacterial; Genetic Complementation Test; Humans; Isoenzymes/genetics; Isoenzymes/metabolism; Molecular Sequence Data; Mutagenesis; Rabbits; Sequence Analysis, DNA; Streptonigrin/pharmacology; Transcription, Genetic; Xanthomonas campestris/drug effects; Xanthomonas campestris/enzymology; Xanthomonas campestris/genetics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
XANCB:B0RSR5	enables	GO:0003994: aconitate hydratase activity	ECO:0000315: mutant phenotype evidence used in manual assertion		F		Seeded From UniProt	complete
XANCB:B0RSR5		GO:0003994: aconitate hydratase activity	ECO:0000315:		F		Figure 2 shows a zymogram of the aconitase activity of the wild type in lane one, and the complemented rpfA mutant in lane three.	complete CACAO 9726

References

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