title: Glutathione-dependent alcohol dehydrogenase AdhC is required for defense against nitrosative stress in Haemophilus influenzae.
abstract: In Haemophilus influenzae Rd KW20, we identified a gene, adhC, which encodes a class III alcohol dehydrogenase (AdhC) and has S-nitrosoglutathione reductase activity. adhC exists on an operon with estD, which encodes an esterase. Divergent to the adhC-estD operon is the Haemophilus influenzae nmlR gene (nmlR(HI)), which encodes a MerR family regulator that is homologous to the Neisseria MerR-like regulator (NmlR). Analysis of an nmlR(HI) mutant indicated that expression of the adhC-estD operon is regulated by NmlR(HI) in strain Rd KW20. Chromosomal inactivation of either adhC or nmlR(HI) resulted in sensitivity to S-nitrosoglutathione and decreased S-nitrosoglutathione reductase activity. Examination of the NmlR(HI)-AdhC system in the genome sequences of nontypeable H. influenzae strains R2846, R2866, and 86-028NP identified significant variations. The adhC gene of 86-028NP was predicted to be nonfunctional due to a premature stop codon. Polymorphisms in the operator/promoter region of R2866 resulted in reduced enzyme activity. This correlated with an increased sensitivity to S-nitrosoglutathione. The adhC-nmlR(HI) system was examined in thirty-three clinical isolates (both capsular and nontypeable strains). Nucleic acid sequence data showed that only strain 86-028NP contained a premature stop codon. There were some variations in the DNA sequence of the operator/promoter region which altered the nmlR(HI) promoter. However, the clinical isolates still possessed S-nitrosoglutathione reductase activity and showed at least the equivalent ability to grow in the presence of S-nitrosoglutathione as Rd KW20. These data suggest that the nmlR(HI)-adhC system has a role in the defense against nitrosative stress in Haemophilus influenzae.
authors.affiliation: Australian Bacterial Pathogenesis Program and Centre for Metals in Biology, School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Kidd
authors.forename: Donald
authors.initials: D
authors.lastname: Jiang
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jennings
authors.forename: Alastair G
authors.initials: AG
authors.lastname: McEwan
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000502:physiology*; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006193:Haemophilus influenzae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D018384:Oxidative Stress / Q000502:physiology*; D026361:Reactive Nitrogen Species / Q000378:metabolism*; D026422:S-Nitrosoglutathione / Q000494:pharmacology*; D014157:Transcription Factors / Q000502:physiology
chemical_list: D026361:Reactive Nitrogen Species; D014157:Transcription Factors; D026422:S-Nitrosoglutathione; C020145:formaldehyde dehydrogenase (glutathione); D000445:Aldehyde Oxidoreductases; C087006:formaldehyde dehydrogenase, glutathione-independent