Only one catalase, katG, is detectable in Rhizobium etli, and is encoded along with the regulator OxyR on a plasmid replicon

1 Programa de Ingeniería Metabólica, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos, CP62210, Mexico 2 Programa de Genética Molecular de Plásmidos Bacterianos, Centro de Investigación sobre Fijación de Nitrógeno,...

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Published in:Microbiology (Society for General Microbiology) 2003-05, Vol.149 (5), p.1165-1176
Main Authors: del Carmen Vargas, Maria, Encarnacion, Sergio, Davalos, Araceli, Reyes-Perez, Agustin, Mora, Yolanda, Garcia-de los Santos, Alejandro, Brom, Susana, Mora, Jaime
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Bacteriology
Biological and medical sciences
Catalase - genetics
Catalase - metabolism
DNA-Binding Proteins
Fundamental and applied biological sciences. Psychology
Gene Expression Regulation, Bacterial
Hydrogen Peroxide - pharmacology
katG gene
KatG protein
Microbiology
Miscellaneous
Molecular Sequence Data
Nitrogen Fixation
Phaseolus - microbiology
Phaseolus vulgaris
Plasmids
Replicon
Repressor Proteins - genetics
Repressor Proteins - metabolism
Rhizobium - enzymology
Rhizobium - genetics
Rhizobium - growth & development
Rhizobium etli
Sequence Analysis, DNA
Symbiosis
Transcription Factors - genetics
Transcription Factors - metabolism
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Summary:1 Programa de Ingeniería Metabólica, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos, CP62210, Mexico 2 Programa de Genética Molecular de Plásmidos Bacterianos, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos, CP62210, Mexico Correspondence Sergio Encarnación encarnac{at}cifn.unam.mx The plasmid-borne Rhizobium etli katG gene encodes a dual-function catalase-peroxidase (KatG) (EC 1.11.1.7) that is inducible and heat-labile. In contrast to other rhizobia, katG was shown to be solely responsible for catalase and peroxidase activity in R. etli . An R. etli mutant that did not express catalase activity exhibited increased sensitivity to hydrogen peroxide (H 2 O 2 ). Pre-exposure to a sublethal concentration of H 2 O 2 allowed R. etli to adapt and survive subsequent exposure to higher concentrations of H 2 O 2 . Based on a multiple sequence alignment with other catalase-peroxidases, it was found that the catalytic domains of the R. etli KatG protein had three large insertions, two of which were typical of KatG proteins. Like the katG gene of Escherichia coli , the R. etli katG gene was induced by H 2 O 2 and was important in sustaining the exponential growth rate. In R. etli , KatG catalase-peroxidase activity is induced eightfold in minimal medium during stationary phase. It was shown that KatG catalase-peroxidase is not essential for nodulation and nitrogen fixation in symbiosis with Phaseolus vulgaris , although bacteroid proteome analysis indicated an alternative compensatory mechanism for the oxidative protection of R. etli in symbiosis. Next to, and divergently transcribed from the catalase promoter, an ORF encoding the regulator OxyR was found; this is the first plasmid-encoded oxyR gene described so far. Additionally, the katG promoter region contained sequence motifs characteristic of OxyR binding sites, suggesting a possible regulatory mechanism for katG expression. Abbreviations: SOD, superoxide dismutase The katG and oxyR sequences discussed in this study have been deposited in GenBank under accession number AF486647 .
ISSN:1350-0872
1465-2080
DOI:10.1099/mic.0.25909-0