Inactivation of thioredoxin-like gene alters oxidative stress resistance and reduces cytochrome c oxidase activity in Agrobacterium tumefaciens

Abstract

Thioredoxin-like protein (TlpA) is a membrane-anchored periplasmic protein that contains a thioredoxin domain at its C-terminus. An Agrobacterium tumefaciens mutant lacking functional tlpA shows increased sensitivity to a superoxide generator, increased resistance to H2O2, and reduced cytochrome c oxidase activity. Whereas the levels of antioxidant enzymes, including total superoxide dismutase (SOD) and catalases, are unaltered, high expression of periplasmic SOD partially restores the superoxide hypersensitivity of the mutant, suggesting an accumulation of superoxide anions in the periplasm. The change in the ability of the mutant to cope with H 2O2 stress is independent of OxyR, an H2O 2 sensor and transcription regulator. The presented data indicate that TlpA not only is involved in the proper assembly of cytochrome c but is also implicated in the bacterial oxidative stress response. © 2009 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.