scholarly journals Mechanistic insights into Escherichia coli alkyl hydroperoxide reductase complex formation

2017 ◽  
Author(s):  
◽  
Wilson Nartey
Keyword(s):  
Escherichia Coli ◽  
Complex Formation ◽  
Alkyl Hydroperoxide Reductase ◽  
Alkyl Hydroperoxide

Low resolution solution structure of an enzymatic active AhpC 10 :AhpF 2 ensemble of the Escherichia coli Alkyl hydroperoxide Reductase

2016 ◽  
Vol 193 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Neelagandan Kamariah ◽  
Wilson Nartey ◽  
Birgit Eisenhaber ◽  
Frank Eisenhaber ◽  
Gerhard Grüber
Keyword(s):  
Escherichia Coli ◽  
Solution Structure ◽  
Low Resolution ◽  
Alkyl Hydroperoxide Reductase ◽  
Alkyl Hydroperoxide

scholarly journals Role of OxyR as a Peroxide-Sensing Positive Regulator in Streptomyces coelicolor A3(2)

2002 ◽  
Vol 184 (19) ◽  
pp. 5214-5222 ◽  
Author(s):  
Ji-Sook Hahn ◽  
So-Young Oh ◽  
Jung-Hye Roe
Keyword(s):  
Escherichia Coli ◽  
Streptomyces Coelicolor ◽  
Cumene Hydroperoxide ◽  
Exponential Phase ◽  
Alkyl Hydroperoxide Reductase ◽  
Direct Role ◽  
Positive Regulator ◽  
Alkyl Hydroperoxide ◽  
Serovar Typhimurium ◽  
Genes Encoding

ABSTRACT 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 phase. Overproduction of OxyR in Streptomyces lividans conferred resistance against cumene hydroperoxide and H2O2. The oxyR mutant produced fewer ahpCD and oxyR transcripts than the wild type, suggesting that OxyR acts as a positive regulator for their expression. Both oxyR and ahpCD transcripts increased more than fivefold within 10 min of H2O2 treatment and decreased to the normal level in 50 min, with kinetics similar to those of the CatR-mediated induction of the catalase A gene (catA) by H2O2. The oxyR mutant failed to induce oxyR and ahpCD genes in response to H2O2, indicating that OxyR is the modulator for the H2O2-dependent induction of these genes. Purified OxyR protein bound specifically to the intergenic region between ahpC and oxyR, suggesting its direct role in regulating these genes. These results demonstrate that in S. coelicolor OxyR mediates H2O2 induction of its own gene and genes for alkyl hydroperoxide reductase system, but not the catalase gene (catA), unlike in Escherichia coli and Salmonella enterica serovar Typhimurium.

scholarly journals Alkyl Hydroperoxide Reductase Is the Primary Scavenger of Endogenous Hydrogen Peroxide in Escherichia coli

2001 ◽  
Vol 183 (24) ◽  
pp. 7173-7181 ◽  
Author(s):  
Lauren Costa Seaver ◽  
James A. Imlay
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Candidate Genes ◽  
Residual Activity ◽  
Aerobic Metabolism ◽  
Scavenging Activity ◽  
Wild Type ◽  
Alkyl Hydroperoxide Reductase ◽  
E Coli ◽  
Alkyl Hydroperoxide

ABSTRACT Hydrogen peroxide is generated during aerobic metabolism and is capable of damaging critical biomolecules. However, mutants ofEscherichia coli that are devoid of catalase typically exhibit no adverse phenotypes during growth in aerobic media. We discovered that catalase mutants retain the ability to rapidly scavenge H2O2 whether it is formed internally or provided exogenously. Analysis of candidate genes revealed that the residual activity is due to alkyl hydroperoxide reductase (Ahp). Mutants that lack both Ahp and catalase could not scavenge H2O2. These mutants excreted substantial amounts of H2O2, and they grew poorly in air. Ahp is kinetically a more efficient scavenger of trace H2O2 than is catalase and therefore is likely to be the primary scavenger of endogenous H2O2. Accordingly, mutants that lack Ahp accumulated sufficient hydrogen peroxide to induce the OxyR regulon, whereas the OxyR regulon remained off in catalase mutants. Catalase still has an important role in wild-type cells, because the activity of Ahp is saturated at a low (10−5 M) concentration of H2O2. In contrast, catalase has a high K m , and it therefore becomes the predominant scavenger when H2O2 concentrations are high. This arrangement is reasonable because the cell cannot provide enough NADH for Ahp to rapidly degrade large amounts of H2O2. In sum,E. coli does indeed generate substantial H2O2, but damage is averted by the scavenging activity of Ahp.

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