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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Since they are equipped with several strategies by which they evade the antimicrobial defense of host macrophages, it is surprising that members of the genus Haemophilus appear to be deficient in common antioxidant systems that are well established to protect prokaryotes against oxidative stress. Among others, no genetic evidence for glutathione (gamma-Glu-Cys-Gly) (GSH) biosynthesis or for alkyl hydroperoxide reduction (e.g., the Ahp system characteristic or enteric bacteria) is apparent from the Haemophilus influenzae Rd genome sequence, suggesting that the organism relies on alternative systems to maintain redox homeostasis or to reduce small alkyl hydroperoxides. In this report we address this apparent paradox for the nontypeable H. influenzae type strain NCTC 8143. Instead of biosynthesis, we could show that this strain acquires GSH by importing the thiol tripeptide from the growth medium. Although such GSH accumulation had no effect on growth rates, the presence of cellular GSH protected against methylglyoxal, tert-butyl hydroperoxide (t-BuOOH), and S-nitrosoglutathione toxicity and regulated the activity of certain antioxidant enzymes. H. influenzae NCTC 8143 extracts were shown to contain GSH-dependent peroxidase activity with t-BuOOH as the peroxide substrate. The GSH-mediated protection against t-BuOOH stress is most probably catalyzed by the product of open reading frame HI0572 (Prx/Grx), which we isolated from a genomic DNA fragment that confers wild-type resistance to t-BuOOH toxicity in the Ahp-negative Escherichia coli strain TA4315 and that introduces GSH-dependent alkyl hydroperoxide reductase activity into naturally GSH peroxidase-negative E. coli. Finally, we demonstrated that cysteine is an essential amino acid for growth and that cystine, GSH, glutathione amide, and cysteinylglycine can be catabolized in order to complement cysteine deficiency.
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PMID:Exogenous glutathione completes the defense against oxidative stress in Haemophilus influenzae. 1259 74

Recently, novel hybrid thiol peroxidase (TPx) proteins fused with a glutaredoxin (Grx) were found from some pathogenic bacteria, cyanobacteria, and anaerobic sulfur-oxidizing phototroph. The phylogenic tree analysis that was constructed from the aligned sequences showed two major branches. Haemophilus influenzae TPx.Grx was grouped in one branch as a 1-Cys subfamily of the thiol-specific antioxident protein/AhpC family. Most TPx.Grx proteins, including Vibrio cholerae TPx.Grx, were grouped in the 2-Cys subfamily. To explain the existence of two subgroups in novel hybrid TPx proteins, we have compared the kinetics given by V. cholerae TPx.Grx, H. influenzae TPx.Grx, their separated TPx domains, and a set of mutants devoid of the redox-active cysteines. The kinetic study described here demonstrates clearly that V. cholerae TPx.Grx is a 2-Cys TPx subfamily. For the first time, we also demonstrate the lipid peroxidase activity of V. cholerae TPx.Grx fusion and suggest the in vivo function of 2-Cys TPx.Grx fusion serving as a lipid peroxidase.
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PMID:Vibrio cholerae thiol peroxidase-glutaredoxin fusion is a 2-Cys TSA/AhpC subfamily acting as a lipid hydroperoxide reductase. 1470 41

Glutaredoxins (Grx) represent a large family of glutathione (GSH)-dependent oxidoreductases that catalyse the reduction of disulfides or glutathione mixed disulfide. Grx domains from pathogenic bacteria and plant Grxs have been recently reported to target specific peroxiredoxins (Prxs). The specificity that triggers the interaction between Grx and Prx is poorly understood and is only based on the structure of Haemophilus influenzae Prx-Grx hybrid (hyPrx5). We report here an NMR study of the Populus tremula Grx C4 that targets a P.tremula D-type II Prx. We show that Grx C4 specifically self-associates in a monomer-dimer equilibrium with an apparent K(d) of ca 2.6 mM. Grx C4 homodimer was docked under experimental restraints. The results reveal a novel Grx-Grx interface that is unrelated to the hyPrx5 Grx-Grx dimer interface. Chemical-shift perturbations and 15N spin-relaxation measurements show that the auto-association surface comprises both the active site and the GSH binding site. Reduced GSH is demonstrated to bind reduced Grx with a K(d) of ca 8.6 mM. The potential biological significance of the new Grx-Grx interaction interface is discussed.
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PMID:NMR reveals a novel glutaredoxin-glutaredoxin interaction interface. 1618 38