title: Nitric oxide regulated two-component signaling in Pseudoalteromonas atlantica.
abstract: Bacteria employ two-component signaling to detect and respond to environmental stimuli. In essence, two-component signaling relies on a protein called a response regulator that can elicit a change in gene expression or protein function in response to phosphoryl transfer from a histidine kinase. Phosphorylation of the associated histidine kinase is regulated by detection of an environmental signal, thus linking sensing to cellular response. Recently, it has been suggested that H-NOX (Heme-nitric oxide/oxygen binding) proteins may act as nitric oxide (NO) sensors in two-component signaling systems. NO/H-NOX regulated histidine kinases have been reported, but their cognate response regulators have yet to be identified. In this work we provide biochemical characterization of a complete NO/H-NOX-regulated two-component signaling pathway in the biofilm-dwelling marine bacterium, Pseudoalteromonas atlantica. In P. atlantica, as is typical for bacteria that code for H-NOX, an hnoX gene is found in the same operon as a gene coding for a two-component signaling histidine kinase (H-NOX-associated histidine kinase; HahK). We find that HahK is capable of autophosphorylation in vitro and that NO-bound H-NOX inhibits HahK activity, implicating H-NOX as a selective NO sensor. The cognate response regulator, a protein annotated as a cyclic-di-GMP processing enzyme that we have named HarR (H-NOX-associated response regulator), was identified using bioinformatics tools. Phosphoryl transfer from HahK to HarR has been established. This report reveals the first biochemical characterization of an H-NOX-associated response regulator and contributes to a deeper understanding of NO/H-NOX signaling in bacteria.
authors.affiliation: Department of Chemistry and the Institute of Chemical Biology and Drug Discovery, Stony Brook University, Stony Brook, NY 11794-3400, USA.
authors.forename: Dhruv P
authors.initials: DP
authors.lastname: Arora
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Boon
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006418:Heme / Q000378:metabolism*; D000071677:Histidine Kinase; D009569:Nitric Oxide / Q000378:metabolism*; D009876:Operon; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D031161:Pseudoalteromonas / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D009569:Nitric Oxide; D006418:Heme; D011494:Protein Kinases; D000071677:Histidine Kinase; D010744:Phosphoric Monoester Hydrolases