A Novel Heme Protein That Acts as a Carbon Monoxide-Dependent Transcriptional Activator inRhodospirillum rubrum

Aono, Shigetoshi; Nakajima, Hiroshi; Saito, Kimio; Okada, M.

doi:10.1006/bbrc.1996.1727

Cited by 115 publications

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“…Heme proteins are used by some bacteria, for example, Rhodospirillum rubrum (18), to sense CO. We therefore examined whether CO had any effect on DosS autokinase activity. We found that exposure of met DosS to CO did not generate any further autokinase activity.…”

Section: Doss Is In the Metmentioning

confidence: 99%

Mycobacterium tuberculosis DosS is a redox sensor and DosT is a hypoxia sensor

Kumar¹,

Toledo

Patel

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

297

375

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A fundamental challenge to the study of oxidative stress responses of Mycobacterium tuberculosis (Mtb) is to understand how the protective host molecules are sensed and relayed to control bacilli gene expression. The genetic response of Mtb to hypoxia and NO is controlled by the sensor kinases DosS and DosT and the response regulator DosR through activation of the dormancy/NO (Dos) regulon. However, the regulatory ligands of DosS and DosT and the mechanism of signal sensing were unknown. Here, we show that both DosS and DosT bind heme as a prosthetic group and that DosS is rapidly autooxidized to attain the met (Fe 3؉ ) form, whereas DosT exists in the O 2-bound (oxy) form. EPR and UV-visible spectroscopy analysis showed that O 2, NO, and CO are ligands of DosS and DosT. Importantly, we demonstrate that the oxidation or ligation state of the heme iron modulates DosS and DosT autokinase activity and that ferrous DosS, and deoxy DosT, show significantly increased autokinase activity compared with met DosS and oxy DosT. Our data provide direct proof that DosS functions as a redox sensor, whereas DosT functions as a hypoxia sensor, and that O 2, NO, and CO are modulatory ligands of DosS and DosT. Finally, we identified a third potential dormancy signal, CO, that induces the Mtb Dos regulon. We conclude that Mtb has evolved finely tuned redox and hypoxia-mediated sensing strategies for detecting O 2, NO, and CO. Data presented here establish a paradigm for understanding the mechanism of bacilli persistence.carbon monoxide ͉ dormancy ͉ nitric oxide ͉ oxygen ͉ persistence T uberculosis (TB) is a major global health burden, and current estimates suggest that one-third of the world's population (Ϸ2 billion) is latently infected with TB (1). Latency is important largely because persistent Mycobacterium tuberculosis (Mtb) are in a state of ''drug unresponsiveness'' wherein the bacilli are resistant to existing antimycobacterial drugs. A major question in the TB field is: ''what are the mechanisms that allow Mtb to persist in human tissues for decades without replicating, to then abruptly resume growth and cause disease?'' Addressing that question is essential to the development of effective therapeutic intervention strategies. Recent evidence implicates NO as an environmental trigger of mycobacterial persistence (2-5). The latter findings are particularly interesting in light of the fact that inducible NO synthase (iNOS) and therefore NO production is crucial for protection of mice against Mtb (6), and that human macrophages in Mtb-infected tissues express iNOS (2, 7). Another factor associated with latent TB is hypoxia (8). The role of oxygen tension in TB is receiving wide attention, especially because it was demonstrated that rapid withdrawal of oxygen is lethal to Mtb, whereas a gradual depletion allows time for adaptation and bacterial survival (8). Interestingly, a significant overlap exists between the gene expression profiles of Mtb cells treated with NO and that of bacilli cultured under hypoxic conditions (3-5). ...

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Section: Doss Is In the Metmentioning

confidence: 99%

Mycobacterium tuberculosis DosS is a redox sensor and DosT is a hypoxia sensor

Kumar¹,

Toledo

Patel

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

297

375

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“…Previous studies on several bacterial species suggest that Crp/Fnr regulators are involved in responses to a variety of intracellular or extracellular signals, such as anoxia, carbon monoxide, temperature, nitric oxide, and oxidative and nitrosative stress (1,13,35,42) and control metabolic pathways such as photosynthesis, nitrogen fixation, aromatic compound degradation, and respiration (11,25,31,39).…”

mentioning

confidence: 99%

Functional Characterization of Crp/Fnr-Type Global Transcriptional Regulators in Desulfovibrio vulgaris Hildenborough

Zhou

Chen

Zane

et al. 2012

Appl Environ Microbiol

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Crp/Fnr-type global transcriptional regulators regulate various metabolic pathways in bacteria and typically function in response to environmental changes. However, little is known about the function of four annotated Crp/Fnr homologs (DVU0379, DVU2097, DVU2547, and DVU3111) in Desulfovibrio vulgaris Hildenborough. A systematic study using bioinformatic, transcriptomic, genetic, and physiological approaches was conducted to characterize their roles in stress responses. Similar growth phenotypes were observed for the crp/fnr deletion mutants under multiple stress conditions. Nevertheless, the idea of distinct functions of Crp/Fnr-type regulators in stress responses was supported by phylogeny, gene transcription changes, fitness changes, and physiological differences. The four D. vulgaris Crp/Fnr homologs are localized in three subfamilies (HcpR, CooA, and cc). The crp/fnr knockout mutants were well separated by transcriptional profiling using detrended correspondence analysis (DCA), and more genes significantly changed in expression in a ⌬DVU3111 mutant (JW9013) than in the other three paralogs. In fitness studies, strain JW9013 showed the lowest fitness under standard growth conditions (i.e., sulfate reduction) and the highest fitness under NaCl or chromate stress conditions; better fitness was observed for a ⌬DVU2547 mutant (JW9011) under nitrite stress conditions and a ⌬DVU2097 mutant (JW9009) under air stress conditions. A higher Cr(VI) reduction rate was observed for strain JW9013 in experiments with washed cells. These results suggested that the four Crp/Fnr-type global regulators play distinct roles in stress responses of D. vulgaris. DVU3111 is implicated in responses to NaCl and chromate stresses, DVU2547 in nitrite stress responses, and DVU2097 in air stress responses.T ranscription factors, promoter sequences, and regulatory circuit architecture are often referred as "the regulatory genome" (27, 33), and transcription factors are central to the function of regulatory networks (5). Organisms rely on regulatory networks to orchestrate the transcription of genes in response to internal or external environmental changes in order to optimize metabolism and enhance survival. Crp/Fnr regulators are global transcriptional regulators widely distributed in bacteria. The characteristic structure of Crp/Fnr is a C-terminal helix-turn-helix (HTH) motif that fits the DNA major groove and an N-terminal nucleotide binding domain (34). This class of transcriptional factors is named after the first two representatives discovered in Escherichia coli, i.e., the Crp (cyclic AMP [cAMP] receptor protein) and Fnr (fumarate and nitrate reductase regulator protein) (4, 21, 24, 27). Crp/Fnr regulators are generally classified into different subfamilies (e.g., CooA, Crp, Dnr, FixK, Fnr, HbaR, NnrR, etc.) according to phylogenetic affiliations (50). The increasing number of sequenced whole genomes has added to a growing list of Crp/Fnr family regulators identified in bacteria (9, 26); however, functions for most are not well defin...

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“…CooA is one of the heme proteins that act as a DNA-binding transcriptional activator (1,2). The purple, nonsulfur, phototrophic bacterium Rhodospirillum rubrum synthesizes a series of enzymes that oxidize carbon monoxide (CO) into carbon dioxide, which is coupled to the evolution of molecular hydrogen (3).…”

mentioning

confidence: 99%

“…Unlike other bacteria capable of oxidizing CO anaerobically, R. rubrum expresses the CO-oxidizing enzymes only in the presence of atmospheric CO (4). A gene region designated as cooA was demonstrated to be responsible for the regulation, whose product protein, CooA, shows high homology with the known transcriptional regulators, such as cyclic AMP receptor protein (CRP) 1 (28% identical, 51% similar) (4). Like the mechanism of CRP activation by cyclic AMP, CO is assumed to bind with CooA (3,(5)(6)(7)(8)(9)(10), which causes the protein-CO complex to bind specifically to the target DNA, resulting in the expression of CO oxidizing enzymes (7,10).…”

mentioning

confidence: 99%

“…Recent success of the high level expression of CooA in Escherichia coli has enabled us and other researchers to obtain enough homogeneous protein for spectroscopic investigations (1,2). It was revealed that each subunit of CooA contains a single b-type heme as a prosthetic group, which can bind exogenous CO reversibly, as is evidenced by its optical absorption spectra (1,2).…”

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confidence: 99%

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Heme Environmental Structure of CooA Is Modulated by the Target DNA Binding

Uchida

Ishikawa

Takahashi

et al. 1998

Journal of Biological Chemistry

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In order to investigate the gene activation mechanism triggered by the CO binding to CooA, a heme-containing transcriptional activator, the heme environmental structure and the dynamics of the CO rebinding and dissociation have been examined in the absence and presence of its target DNA. In the absence of DNA, the Fe-CO and C‫؍‬O stretching Raman lines of the CO-bound CooA were observed at 487 and 1969 cm ؊1 , respectively, suggesting that a neutral histidine is an axial ligand trans to CO. The frequency of (Fe-CO) implies an open conformation of the distal heme pocket, indicating that the ligand replaced by CO is located away from the bound CO. When the target DNA was added to CO-bound CooA, an appearance of a new (Fe-CO) line at 519 cm ؊1 and narrowing of the main line at 486 cm ؊1 were observed. Although the rate of the CO dissociation was insensitive to the additions of DNA, the CO rebinding was decelerated in the presence of the target DNA, but not in the presence of nonsense DNA. These observations demonstrate the structural alterations in the heme distal site in response to binding of the target DNA and support the activation mechanism proposed for CooA, which is triggered by the movement of the heme distal ligand to modify the conformation of the DNA binding domain.

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A Novel Heme Protein That Acts as a Carbon Monoxide-Dependent Transcriptional Activator inRhodospirillum rubrum

Cited by 115 publications

References 0 publications

Mycobacterium tuberculosis DosS is a redox sensor and DosT is a hypoxia sensor

Mycobacterium tuberculosis DosS is a redox sensor and DosT is a hypoxia sensor

Functional Characterization of Crp/Fnr-Type Global Transcriptional Regulators in Desulfovibrio vulgaris Hildenborough

Heme Environmental Structure of CooA Is Modulated by the Target DNA Binding

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