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Busche T, Winkler A, Wedderhoff I, Rückert C, Kalinowski J, Ortiz de Orué Lucana D. Deciphering the Transcriptional Response Mediated by the Redox-Sensing System HbpS-SenS-SenR from Streptomycetes. PLoS One 2016; 11:e0159873. [PMID: 27541358 PMCID: PMC4991794 DOI: 10.1371/journal.pone.0159873] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 07/08/2016] [Indexed: 12/30/2022] Open
Abstract
The secreted protein HbpS, the membrane-embedded sensor kinase SenS and the cytoplasmic response regulator SenR from streptomycetes have been shown to form a novel type of signaling pathway. Based on structural biology as well as different biochemical and biophysical approaches, redox stress-based post-translational modifications in the three proteins were shown to modulate the activity of this signaling pathway. In this study, we show that the homologous system, named here HbpSc-SenSc-SenRc, from the model species Streptomyces coelicolor A3(2) provides this bacterium with an efficient defense mechanism under conditions of oxidative stress. Comparative analyses of the transcriptomes of the Streptomyces coelicolor A3(2) wild-type and the generated hbpSc-senSc-senRc mutant under native and oxidative-stressing conditions allowed to identify differentially expressed genes, whose products may enhance the anti-oxidative defense of the bacterium. Amongst others, the results show an up-regulated transcription of genes for biosynthesis of cysteine and vitamin B12, transport of methionine and vitamin B12, and DNA synthesis and repair. Simultaneously, transcription of genes for degradation of an anti-oxidant compound is down-regulated in a HbpSc-SenSc-SenRc-dependent manner. It appears that HbpSc-SenSc-SenRc controls the non-enzymatic response of Streptomyces coelicolor A3(2) to counteract the hazardous effects of oxidative stress. Binding of the response regulator SenRc to regulatory regions of some of the studied genes indicates that the regulation is direct. The results additionally suggest that HbpSc-SenSc-SenRc may act in concert with other regulatory modules such as a transcriptional regulator, a two-component system and the Streptomyces B12 riboswitch. The transcriptomics data, together with our previous in vitro results, enable a profound characterization of the HbpS-SenS-SenR system from streptomycetes. Since homologues to HbpS-SenS-SenR are widespread in different actinobacteria with ecological and medical relevance, the data presented here will serve as a basis to elucidate the biological role of these homologues.
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Affiliation(s)
- Tobias Busche
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Universitätsstraße 27, 33615, Bielefeld, Germany
| | - Anika Winkler
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Universitätsstraße 27, 33615, Bielefeld, Germany
| | - Ina Wedderhoff
- Applied Genetics of Microorganisms, Department of Biology and Chemistry, University of Osnabrueck, Osnabrueck, Barbarastraße 13, 49076, Osnabrueck, Germany
| | - Christian Rückert
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Universitätsstraße 27, 33615, Bielefeld, Germany
| | - Jörn Kalinowski
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Universitätsstraße 27, 33615, Bielefeld, Germany
| | - Darío Ortiz de Orué Lucana
- Applied Genetics of Microorganisms, Department of Biology and Chemistry, University of Osnabrueck, Osnabrueck, Barbarastraße 13, 49076, Osnabrueck, Germany
- * E-mail:
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Ortiz de Orué Lucana D, Fedosov SN, Wedderhoff I, Che EN, Torda AE. The extracellular heme-binding protein HbpS from the soil bacterium Streptomyces reticuli is an aquo-cobalamin binder. J Biol Chem 2014; 289:34214-28. [PMID: 25342754 PMCID: PMC4256353 DOI: 10.1074/jbc.m114.585489] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 10/22/2014] [Indexed: 11/06/2022] Open
Abstract
The extracellular protein HbpS from Streptomyces reticuli interacts with iron ions and heme. It also acts in concert with the two-component sensing system SenS-SenR in response to oxidative stress. Sequence comparisons suggested that the protein may bind a cobalamin. UV-visible spectroscopy confirmed binding (Kd = 34 μm) to aquo-cobalamin (H2OCbl(+)) but not to other cobalamins. Competition experiments with the H2OCbl(+)-coordinating ligand CN(-) and comparison of mutants identified a histidine residue (His-156) that coordinates the cobalt ion of H2OCbl(+) and substitutes for water. HbpS·Cobalamin lacks the Asp-X-His-X-X-Gly motif seen in some cobalamin binding enzymes. Preliminary tests showed that a related HbpS protein from a different species also binds H2OCbl(+). Furthermore, analyses of HbpS-heme binding kinetics are consistent with the role of HbpS as a heme-sensor and suggested a role in heme transport. Given the high occurrence of HbpS-like sequences among Gram-positive and Gram-negative bacteria, our findings suggest a great functional versatility among these proteins.
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Affiliation(s)
- Darío Ortiz de Orué Lucana
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany,
| | - Sergey N Fedosov
- Department of Engineering, Aarhus University, 8000 Aarhus, Denmark, and
| | - Ina Wedderhoff
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany
| | - Edith N Che
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany
| | - Andrew E Torda
- Centre for Bioinformatics, Hamburg University, 20146 Hamburg, Germany
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Iron binding at specific sites within the octameric HbpS protects streptomycetes from iron-mediated oxidative stress. PLoS One 2013; 8:e71579. [PMID: 24013686 PMCID: PMC3754957 DOI: 10.1371/journal.pone.0071579] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 07/08/2013] [Indexed: 12/26/2022] Open
Abstract
The soil bacterium Streptomyces reticuli secretes the octameric protein HbpS that acts as a sensory component of the redox-signalling pathway HbpS-SenS-SenR. This system modulates a genetic response on iron- and haem-mediated oxidative stress. Moreover, HbpS alone provides this bacterium with a defence mechanism to the presence of high concentrations of iron ions and haem. While the protection against haem has been related to its haem-binding and haem-degrading activity, the interaction with iron has not been studied in detail. In this work, we biochemically analyzed the iron-binding activity of a set of generated HbpS mutant proteins and present evidence showing the involvement of one internal and two exposed D/EXXE motifs in binding of high quantities of ferrous iron, with the internal E78XXE81 displaying the tightest binding. We additionally show that HbpS is able to oxidize ferrous to ferric iron ions. Based on the crystal structure of both the wild-type and the mutant HbpS-D78XXD81, we conclude that the local arrangement of the side chains from the glutamates in E78XXE81 within the octameric assembly is a pre-requisite for interaction with iron. The data obtained led us to propose that the exposed and the internal motif build a highly specific route that is involved in the transport of high quantities of iron ions into the core of the HbpS octamer. Furthermore, physiological studies using Streptomyces transformants secreting either wild-type or HbpS mutant proteins and different redox-cycling compounds led us to conclude that the iron-sequestering activity of HbpS protects these soil bacteria from the hazardous side effects of peroxide- and iron-based oxidative stress.
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