AhpF, the alkyl hydroperoxide reductase component which transfers electrons from pyridine nucleotides to the peroxidase protein, AhpC, possesses two redox-active disulfide centers in addition to one FAD per subunit; the primary goal of these studies has been to test for the requirement of one or both of these disulfide centers in catalysis. Two half-cystine residues of one center (Cys345Cys348)...

The AhpC subunit of the Bacillus subtilis alkyl hydroperoxide reductase was identified as a general stress protein induced in response to heat or salt stress or after entry of the organism into the stationary phase. The ahp operon, encoding the two subunits AhpC and AhpF, was cloned and localized between the gntRKPZ operon and the bglA locus. Two-dimensional gel analyses revealed an especially ...

The flavoprotein component (AhpF) of Salmonella typhimurium alkyl hydroperoxide reductase contains an N-terminal domain (NTD) with two contiguous thioredoxin folds but only one redox-active disulfide (within the sequence -Cys129-His-Asn-Cys132-). This active site is responsible for mediating the transfer of electrons from the thioredoxin reductase-like segment of AhpF to AhpC, the peroxiredoxin...

Many eubacterial genomes including those of Salmonella typhimurium, Streptococcus mutans, and Thermus aquaticus encode a dedicated flavoprotein reductase (AhpF, Nox1, or PrxR) just downstream of the structural gene for their peroxiredoxin (Prx, AhpC) homologue to reduce the latter protein during turnover. In contrast, the obligate anaerobe Clostridium pasteurianum codes for a two-component redu...

The catalytic properties of cysteine residues Cys46 and Cys165, which form intersubunit disulfide bonds in the peroxidatic AhpC protein of the alkyl hydroperoxide reductase (AhpR) system from Salmonella typhimurium, have been investigated. The AhpR system, composed of AhpC and a flavoprotein reductase, AhpF, catalyzes the pyridine nucleotide-dependent reduction of organic hydroperoxides and hyd...

In this study we report the identification and role of the alkyl hydroperoxide reductase (ahp) gene in Bacteroides fragilis. The two components of ahp, ahpC, and ahpF, are organized in an operon, and the deduced amino acid sequences revealed that B. fragilis AhpCF shares approximately 60% identity to orthologues in other gram-positive and gram-negative bacteria. Northern blot hybridization anal...

The rate of electron transfer through multicomponent redox systems is often monitored by following the absorbance change due to the oxidation of the upstream pyridine nucleotide electron donor (NADPH or NADH) that initiates the process. Such coupled assay systems are powerful, but because of problems regarding the rate-limiting step, they sometimes limit the kinetic information that can be obta...

The tellurium oxyanion tellurite (TeO3 (2-)) is extremely harmful for most organisms. It has been suggested that a potential bacterial tellurite resistance mechanism would consist of an enzymatic, NAD(P)H-dependent, reduction to the less toxic form elemental tellurium (Te(0)). To date, a number of enzymes such as catalase, type II NADH dehydrogenase and terminal oxidases from the electron trans...

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...

Nox-1 from Streptococcus mutans, the bacteria which cause dental caries, was previously identified as an H2O2-forming reduced nicotinamide adenine dinucleotide (NADH) oxidase. Nox-1 is homologous with the flavoprotein component, AhpF, of Salmonella typhimurium alkyl hydroperoxide reductase. A partial open reading frame upstream of nox1, homologous with the other (peroxidase) component, ahpC, fr...