How Do Heme-Protein Sensors Exclude Oxygen? Lessons Learned from Cytochrome c′,<i>Nostoc puntiforme</i>Heme Nitric Oxide/Oxygen-Binding Domain, and Soluble Guanylyl Cyclase

Tsai, Alan C.; Martin, Emil; Berka, Vladimír; Olson, John S.

doi:10.1089/ars.2012.4564

Cited by 57 publications

(104 citation statements)

References 133 publications

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“…For example, the histidine kinase FixL is inhibited by O 2 but not by CO or NO, even though it binds these two more tightly (29). Protohemes generally bind O 2 , CO, and NO with relative affinities of 1, 10 3 , and 10 6 , respectively (30,31). In this study, we determined that the O 2 and CO affinities of the isolated Aer2 PAS domain are 16 M and 2 M, respectively (Fig.…”

Section: Discussionmentioning

confidence: 71%

Gas Sensing and Signaling in the PAS-Heme Domain of the Pseudomonas aeruginosa Aer2 Receptor

et al. 2017

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The Aer2 chemoreceptor from Pseudomonas aeruginosa contains a PAS sensing domain that coordinates b-type heme and signals in response to the binding of O 2 , CO, or NO. PAS-heme structures suggest that Aer2 uniquely coordinates heme via a His residue on a 3 10 helix (H234 on E), stabilizes O 2 binding via a Trp residue (W283), and signals via both W283 and an adjacent Leu residue (L264). Ligand binding may displace L264 and reorient W283 for hydrogen bonding to the ligand. Here, we clarified the mechanisms by which Aer2-PAS binds heme, regulates ligand binding, and initiates conformational signaling. H234 coordinated heme, but additional hydrophobic residues in the heme cleft were also critical for stable heme binding. O 2 appeared to be the native Aer2 ligand (dissociation constant [K d ] of 16 M). With one exception, mutants that bound O 2 could signal, whereas many mutants that bound CO could not. W283 stabilized O 2 binding but not CO binding, and it was required for signal initiation; W283 mutants that could not stabilize O 2 were rapidly oxidized to Fe(III). W283F was the only Trp mutant that bound O 2 with wildtype affinity. The size and nature of residue 264 was important for gas binding and signaling: L264W blocked O 2 binding, L264A and L264G caused O 2 -mediated oxidation, and L264K formed a hexacoordinate heme. Our data suggest that when O 2 binds to Aer2, L264 moves concomitantly with W283 to initiate the conformational signal. The signal then propagates from the PAS domain to regulate the C-terminal HAMP and kinase control domains, ultimately modulating a cellular response.IMPORTANCE Pseudomonas aeruginosa is a ubiquitous environmental bacterium and opportunistic pathogen that infects multiple body sites, including the lungs of cystic fibrosis patients. P. aeruginosa senses and responds to its environment via four chemosensory systems. Three of these systems regulate biofilm formation, twitching motility, and chemotaxis. The role of the fourth system, Che2, is unclear but has been implicated in virulence. The Che2 system contains a chemoreceptor called Aer2, which contains a PAS sensing domain that binds heme and senses oxygen. Here, we show that Aer2 uses unprecedented mechanisms to bind O 2 and initiate signaling. These studies provide both the first functional corroboration of the Aer2-PAS signaling mechanism previously proposed from structure as well as a signaling model for Aer2-PAS receptors.KEYWORDS chemoreceptor, PAS domain, signal transduction, Pseudomonas aeruginosa, heme, oxygen P seudomonas aeruginosa is a common environmental bacterium and a significant cause of opportunistic human disease. It survives in complex environments with the aid of 26 chemoreceptors and four chemosensory systems that collectively sense environmental conditions and modify bacterial behavior. The roles of three of these chemosensory systems are known: one modulates type IV pili production and twitching motility (Pil-Chp system), another controls biofilm formation (Wsp system), and a third

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Section: Discussionmentioning

confidence: 71%

Gas Sensing and Signaling in the PAS-Heme Domain of the Pseudomonas aeruginosa Aer2 Receptor

et al. 2017

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“…86 In many ferrous nitrosyl complexes, however, NO binding promotes the ejection of the proximal ligand as NO exerts a strong trans effect on ferrous iron, promoting 5-coordinate NO complexes in many hemoproteins, such as sGC and some H-NOX proteins; this process is considered as essential in activating the function of these proteins. 50 A good number of ν (Fe-N)/(N-O) frequencies have been collected for Fe(II)-NO adducts of heme proteins and model compounds in both 5-coordinate and 6-coordinate forms. While relatively low ν (Fe-N) modes are seen for 5-coordinate NO complexes, occurring near ~510–530 cm −1 , with associated N-O frequencies near ~1660–1700 cm −1 , 6-coordinate NO adducts exhibit higher Fe-N frequencies (in the range of ~550–580 cm −1 ) along with higher N-O frequencies ( ~1620–1650 cm −1 ).…”

Section: Resultsmentioning

confidence: 99%

Spectral Characterization of a Novel NO Sensing Protein in Bacteria: NosP

et al. 2018

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A novel family of bacterial hemoproteins named NosP has been discovered recently; its members are proposed to function as nitric oxide (NO) responsive proteins involved in bacterial group behaviors such as quorum sensing and biofilm growth and dispersal. Currently, little is known about molecular activation mechanisms in NosP. Here, functional studies were performed utilizing the distinct spectroscopic characteristics associated with the NosP heme cofactor. NosPs from Pseudomonas aeruginosa (Pa), Vibrio cholerae (Vc) and Legionella pneumophila (Lpg) were studied in their ferrous-unligated forms as well as their ferrous-CO, ferrous-NO, and ferric-CN adducts. The resonance Raman (rR) data collected on the ferric forms strongly support the existence of a distorted heme-cofactor, which is a common feature in NO sensors. The ferrous spectra exhibit a 213 cm−1 feature, which is assigned to the Fe-Nhis stretching mode. The Fe-C and C-O frequencies in the spectra of ferrous-CO NosP complexes are inversely correlated with relatively similar frequencies, consistent with a proximal histidine ligand and a relatively hydrophobic environment. The rR spectra obtained for isotopically labeled ferrous-NO adducts provide evidence of formation of a 5-coordinate NO complex, resulting from proximal Fe-Nhis cleavage, which is believed to play a role in biological heme-NO signal transduction. Additionally, we found that of the three NosPs studied, Lpg NosP contains the most electropositive ligand binding pocket, while Pa NosP has the most electronegative ligand binding pocket. This pattern is also observed in the measured heme reduction potentials for these three proteins, which may indicate distinct functions for each.

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“…The high O 2 affinity for the heme Fe(II) complex, the stability of the heme Fe(II)-O 2 complex, and the role of the Tyr residue (B10) of the distal site in the stability of the O 2 complex are essential contributors to the specific characteristics of GCSs. The sliding scale rule accounts for ligand discrimination of GCS, as well as other gas sensors (92,93).…”

Section: Discussionmentioning

confidence: 99%

Heme-based Globin-coupled Oxygen Sensors: Linking Oxygen Binding to Functional Regulation of Diguanylate Cyclase, Histidine Kinase, and Methyl-accepting Chemotaxis

Martínková

Kitanishi

Shimizu

2013

Journal of Biological Chemistry

107

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An emerging class of novel heme-based oxygen sensors containing a globin fold binds and senses environmental O 2 via a heme iron complex. Structure-function relationships of oxygen sensors containing a heme-bound globin fold are different from those containing heme-bound PAS and GAF folds. It is thus worth reconsidering from an evolutionary perspective how heme-bound proteins with a globin fold similar to that of hemoglobin and myoglobin could act as O 2 sensors. Here, we summarize the molecular mechanisms of heme-based oxygen sensors containing a globin fold in an effort to shed light on the O 2 -sensing properties and O 2 -stimulated catalytic enhancement observed for these proteins.

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How Do Heme-Protein Sensors Exclude Oxygen? Lessons Learned from Cytochrome c′,Nostoc puntiformeHeme Nitric Oxide/Oxygen-Binding Domain, and Soluble Guanylyl Cyclase

Cited by 57 publications

References 133 publications

Gas Sensing and Signaling in the PAS-Heme Domain of the Pseudomonas aeruginosa Aer2 Receptor

Gas Sensing and Signaling in the PAS-Heme Domain of the Pseudomonas aeruginosa Aer2 Receptor

Spectral Characterization of a Novel NO Sensing Protein in Bacteria: NosP

Heme-based Globin-coupled Oxygen Sensors: Linking Oxygen Binding to Functional Regulation of Diguanylate Cyclase, Histidine Kinase, and Methyl-accepting Chemotaxis

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