AnkB, a Periplasmic Ankyrin-Like Protein in Pseudomonas aeruginosa, Is Required for Optimal Catalase B (KatB) Activity and Resistance to Hydrogen Peroxide
AUTOR(ES)
Howell, Michael L.
FONTE
American Society for Microbiology
RESUMO
In this study, we have cloned the ankB gene, encoding an ankyrin-like protein in Pseudomonas aeruginosa. The ankB gene is composed of 549 bp encoding a protein of 183 amino acids that possesses four 33-amino-acid ankyrin repeats that are a hallmark of erythrocyte and brain ankyrins. The location of ankB is 57 bp downstream of katB, encoding a hydrogen peroxide-inducible catalase, KatB. Monomeric AnkB is a 19.4-kDa protein with a pI of 5.5 that possesses 22 primarily hydrophobic amino acids at residues 3 to 25, predicting an inner-membrane-spanning motif with the N terminus in the cytoplasm and the C terminus in the periplasm. Such an orientation in the cytoplasmic membrane and, ultimately, periplasmic space was confirmed using AnkB-BlaM and AnkB-PhoA protein fusions. Circular dichroism analysis of recombinant AnkB minus its signal peptide revealed a secondary structure that is ∼65% α-helical. RNase protection and KatB- and AnkB-LacZ translational fusion analyses indicated that katB and ankB are part of a small operon whose transcription is induced dramatically by H2O2, and controlled by the global transactivator OxyR. Interestingly, unlike the spherical nature of ankyrin-deficient erythrocytes, the cellular morphology of an ankB mutant was identical to that of wild-type bacteria, yet the mutant produced more membrane vesicles. The mutant also exhibited a fourfold reduction in KatB activity and increased sensitivity to H2O2, phenotypes that could be complemented in trans by a plasmid constitutively expressing ankB. Our results suggest that AnkB may form an antioxidant scaffolding with KatB in the periplasm at the cytoplasmic membrane, thus providing a protective lattice work for optimal H2O2 detoxification.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=94626Documentos Relacionados
- Cloning and characterization of the katB gene of Pseudomonas aeruginosa encoding a hydrogen peroxide-inducible catalase: purification of KatB, cellular localization, and demonstration that it is essential for optimal resistance to hydrogen peroxide.
- Bacterioferritin A Modulates Catalase A (KatA) Activity and Resistance to Hydrogen Peroxide in Pseudomonas aeruginosa
- Legionella pneumophila Catalase-Peroxidases: Cloning of the katB Gene and Studies of KatB Function
- Protective Role of Catalase in Pseudomonas aeruginosa Biofilm Resistance to Hydrogen Peroxide
- A 104-kDa diacylglycerol kinase containing ankyrin-like repeats localizes in the cell nucleus.