Little is known about the mechanisms by which Treponema pallidum (Tp), the causative agent of syphilis, copes with oxidative stress as it establishes persistent infection within its obligate human host. The Tp genomic sequence indicates that the bacterium's antioxidant defenses do not include glutathione and are limited to just a few proteins, with only one, TP0509, offering direct defense agai...

We isolated menadione-resistant mutants of Xanthomonas campestris pv. phaseoli oxyR (oxyR(Xp)). The oxyRR2(Xp) mutant was hyperresistant to the superoxide generators menadione and plumbagin and was moderately resistant to H(2)O(2) and tert-butyl hydroperoxide. Analysis of enzymes involved in oxidative-stress protection in the oxyRR2(Xp) mutant revealed a >10-fold increase in AhpC and AhpF level...

Lipid hydroperoxides are highly toxic to biological systems. Here, the Xanthomonas campestris pv. phaseoli sensing and protective systems against linoleic hydroperoxide (LOOH) were investigated by examining the phenotypes, biochemical and regulatory characteristics of various Xanthomonas mutants in known peroxide resistance pathways. Analysis of LOOH resistance levels indicates that both alkyl ...

Magnetic resonance imaging (MRI) features of intracranial anaplastic hemangiopericytoma (AHPC) were analyzed. The pathological examination showed that there was a great number of irregularly arranged tumor cells with nuclear atypia, and mitotic properties were commonly seen providing support for clinical staging, therapy and prognosis judgment. Eighteen cases of intracranial AHPC proved by oper...

Genes encoding a homolog of Escherichia coli OxyR (oxyR) and an alkyl hydroperoxide reductase system (ahpC and ahpD) have been isolated from Streptomyces coelicolor A3(2). The ahpC and ahpD genes constitute an operon transcribed divergently from the oxyR gene. Expression of both ahpCD and oxyR genes was maximal at early exponential phase and decreased rapidly as cells entered mid-exponential ph...

AhpF, the flavoprotein reductase component of the Salmonella typhimurium alkyl hydroperoxide reductase system, catalyzes the reduction of an intersubunit disulfide bond in the peroxidatic active site of the system's other component, AhpC, a member of the peroxiredoxin family. Previous studies have shown that AhpF can be dissected into two functional units, a thioredoxin reductase-like C-terminu...

A gene encoding a putative 2[4Fe--4S] ferredoxin (FdxA) was identified upstream of, and divergent to the peroxide stress defense gene ahpC of the microaerophilic pathogen Campylobacter jejuni. The transcription start site of fdxA was located 27 and 28 bp upstream of the fdxA start codon. Transcriptional fusions of the fdxA promoter to a lacZ reporter gene demonstrated that expression of fdxA is...

To understand how Corynebacterium diphtheriae responds to iron limitation, we compared the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) protein profiles of both wild-type cells and iron uptake mutants grown in either high- or low-iron medium. The removal of iron by ethylene diamine di-(o-hydroxy-phenyl acetic acid) from the growth medium of wild-type cells resulted in in...

background & objectives: although isoniazid is the most efficient in killing the tuberculosis bacilli, resistance to this drug also develops most readily. mutations in katg, inha and ahpc are responsible for isoniazid resistance in a large proportion of tuberculosis cases. the frequency of these mutations varies with population samples, however. this study provided the first molecular character...

Pathways for the reduction of protein disulfide bonds are found in all organisms and are required for the reductive recycling of certain enzymes including the essential protein ribonucleotide reductase. An Escherichia coli strain that lacks both thioredoxin reductase and glutathione reductase grows extremely poorly. Here, we show that a mutation occurring at high frequencies in the gene ahpC, e...