Mechanism of Binding of NO to Soluble Guanylyl Cyclase: Implication for the Second NO Binding to the Heme Proximal Site

Martin, Emil; Berka, Vladimír; Sharina, Iraida; Tsai, Alan C.

doi:10.1021/bi300105s

Cited by 72 publications

(122 citation statements)

References 30 publications

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“…All these assignments are further strengthened by the fact that in the kinetics at 425 nm (Fig. 3D), the τ 1 and τ 3 transitions appear with very low amplitudes, as expected when probing at a wavelength very close to the isobestic point, located at 423-424 nm between the spectra of resting 5c-His sGC and transient 6c-NO sGC as determined from stopped flow (16,34).…”

Section: Resultssupporting

confidence: 61%

“…Recently, the structure of a bacterial domain H-NOX in a nitrosylated state has been resolved with NO bound to the proximal side (40), which reinforces the hypothesis of proximal binding in sGC. Contrastingly, only one experiment to date, based on EPR and isotopic NO detection (34), has provided an indication that this proximal location for NO may indeed occur in sGC, even though, after the fast geminate rebinding in the picosecond range, we did not assign any of the four subsequent transitions to proximal binding because of their spectral characteristics. However, we must discuss this possibility and assess how it may be integrated into our present picture.…”

Section: Discussion Heme Transition Phases No Dynamics and Consequecontrasting

confidence: 64%

“…The fact that the ratio of NO and His rebindings is not determined by their respective kinetic constants indicates that they do not, strictly speaking, compete for binding to the heme. This observation is in accord (albeit not a proof) with NO binding to the proximal heme side (33,34,37), implying that NO must leave the heme pocket to release steric hindrance preventing His rebinding, which is controlled by a rotational energy barrier.…”

Section: Discussion Heme Transition Phases No Dynamics and Consequementioning

confidence: 90%

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Motion of proximal histidine and structural allosteric transition in soluble guanylate cyclase

Yoo

Lamarre

Martin

et al. 2015

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

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We investigated the changes of heme coordination in purified soluble guanylate cyclase (sGC) by time-resolved spectroscopy in a time range encompassing 11 orders of magnitude (from 1 ps to 0.2 s). After dissociation, NO either recombines geminately to the 4-coordinate (4c) heme (τ G1 = 7.5 ps; 97 ± 1% of the population) or exits the heme pocket (3 ± 1%). The proximal His rebinds to the 4c heme with a 70-ps time constant. Then, NO is distributed in two approximately equal populations (1.5%). One geminately rebinds to the 5c heme (τ G2 = 6.5 ns), whereas the other diffuses out to the solution, from where it rebinds bimolecularly (τ = 50 μs with [NO] = 200 μM) forming a 6c heme with a diffusion-limited rate constant of 2 × 10 8 M −1 ·s −1 . In both cases, the rebinding of NO induces the cleavage of the Fe-His bond that can be observed as an individual reaction step. Saliently, the time constant of bond cleavage differs depending on whether NO binds geminately or from solution (τ 5C1 = 0.66 μs and τ 5C2 = 10 ms, respectively). Because the same event occurs with rates separated by four orders of magnitude, this measurement implies that sGC is in different structural states in both cases, having different strain exerted on the Fe-His bond. We show here that this structural allosteric transition takes place in the range 1-50 μs. In this context, the detection of NO binding to the proximal side of sGC heme is discussed.soluble guanylate cyclase | nitric oxide | time-resolved absorption spectroscopy | allostery | protein activation T he soluble guanylate cyclase (sGC), localized in many different cell types, is the receptor of the endogenous messenger nitric oxide (NO) and catalyzes the formation of cGMP from GTP upon activation triggered by NO binding (1, 2). The diatomic messenger NO and sGC play a critical role in several physiological processes: regulation of vascular blood pressure and cardiovascular diseases (3), lung airway relaxation and pulmonary pathologies (4), immune response and inflammatory disorders (5), and tumor progression and apoptosis (6). Thus, sGC is a pharmacological target of very high interest, and several activators have been developed (7,8), leading to the approval of riociguat for the treatment of pulmonary hypertension (9, 10). Because of its pharmacological interest, the mechanisms of activation, deactivation, and regulation of sGC must be deciphered at the molecular level. Despite numerous efforts, the 3D crystal structure of heterodimeric sGC remains unknown, but the heme domain of the sGC β1-subunit [called heme NO/oxygen-binding (H-NOX)] was modeled from the heme domain of bacterial NO sensors (11,12) and the sGC catalytic α1-subunit was modeled from the catalytic α1-subunit of adenylate cyclase (13). Recently, the entire quaternary structure of sGC was reconstructed by inserting individual protein domains into the density envelope of entire single-sGC molecules observed by EM (14), revealing a high flexibility of the sGC dimer. Subsequently, the structural perturbations induced by NO bi...

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Section: Resultssupporting

confidence: 61%

Section: Discussion Heme Transition Phases No Dynamics and Consequecontrasting

confidence: 64%

Section: Discussion Heme Transition Phases No Dynamics and Consequementioning

confidence: 90%

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Motion of proximal histidine and structural allosteric transition in soluble guanylate cyclase

Yoo

Lamarre

Martin

et al. 2015

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

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“…Alternatively, in more rapid reactions in the presence of excess NO, a second NO molecule binds at the proximal side of the heme, displacing the His (E). The distal NO then dissociates, leaving a high GC activity five-coordinate proximally NO-bound form (F; double green circle) (86). The low (D) and high (F) activity five-coordinate NO-bound forms can be distinguished by EPR spectroscopy.…”

Section: Doss and Dostmentioning

confidence: 99%

“…Preincubation of sGC substrate (Mg 2ϩ -GTP) or products (Mg 2ϩ /cGMP/PP i ) with sGC at stoichiometric NO concentrations may also lead to the high activity form (curved arrow), although ATP competes with GTP and can instead lead to formation of a low activity form (likely species D) (73). The low activity NO-bound form (D) may be less stable and more prone to deactivation in a process that may not involve dissociation of the distal NO ligand (73,86). A distinct "desensitization" of sGC to repeated exposure to NO may result from nitrosation of a sGC protein thiol (73).…”

Section: Doss and Dostmentioning

confidence: 99%

Heme Sensor Proteins

Girvan

Munro

2013

Journal of Biological Chemistry

128

116

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Heme is a prosthetic group best known for roles in oxygen transport, oxidative catalysis, and respiratory electron transport. Recent years have seen the roles of heme extended to sensors of gases such as O 2 and NO and cell redox state, and as mediators of cellular responses to changes in intracellular levels of these gases. The importance of heme is further evident from identification of proteins that bind heme reversibly, using it as a signal, e.g. to regulate gene expression in circadian rhythm pathways and control heme synthesis itself. In this minireview, we explore the current knowledge of the diverse roles of heme sensor proteins. Heme-responsive Proteins: Defining FeaturesHeme homeostasis is crucial. Free heme at Ͼ1 M is cytotoxic, mainly by producing reactive oxygen species. Iron intake accounts for only a small proportion of mammalian requirements, so iron recycling (particularly from heme) is critical (1). Tight regulation of heme synthesis/breakdown is needed. Heme regulates its own fate and controls several other biological processes. Heme-responsive proteins elicit cellular responses by binding/debinding heme or via changes in heme ligation (e.g. by gases) or redox state. They can be divided into two classes: nuclear receptor (NR) 2 hemoproteins and heme sensors with no NR function. Each heme-responsive protein has a heme regulatory motif (HRM), usually containing a CP motif (2). The Cys residue of the CP motif is an axial heme ligand. No other residues are conserved across the protein class. The wider relevance of the CP motif is unclear because other hemoproteins (e.g. prostaglandin E 2 synthase, chloroperoxidase, and some cytochromes P450) also have a CP motif. The properties of members of the two main classes are described below. NR HemoproteinsSeveral heme-binding proteins occur in the NR superfamily, which is the largest transcription factor superfamily (summarized in Table 1). NRs bind specific DNA motifs in response to small molecule signaling. They generally share conserved domain architecture, with a DNA-binding region containing two zinc fingers, a ligand-binding domain, and activation domains (3). Usually, ligand binding induces conformational changes that dissociate partner proteins, allowing DNA binding and/or changes to dimerization status or cellular localization that enable the protein to elicit a response. A subfamily of NRs binds heme at their ligand-binding domain and so act as heme sensors, as discussed below. Circadian Rhythm Heme SensorsCircadian rhythms are regulated by feedback loops at transcriptional/translational levels. Heme is critical in this process (4). In vertebrates, the expression of several day/night cycle genes, as well as Rev-erb␣, is controlled by binding a heterodimer of Clock (or NPAS2 (neuronal PAS domain protein 2)) and Bmal1 to their 5Ј-UTR, thus switching on transcription. Expression of Bmal1 and NPAS2/Clock is repressed in turn by binding of Rev-erb␣ to a homodimeric partner (5). Rev-erb␣ and homologs (Rev-erb␤ and E75, with the latter involved in inse...

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Molecular Mechanisms of Actions for CO

2022

Carbon Monoxide in Drug Discovery

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Mechanism of Binding of NO to Soluble Guanylyl Cyclase: Implication for the Second NO Binding to the Heme Proximal Site

Cited by 72 publications

References 30 publications

Motion of proximal histidine and structural allosteric transition in soluble guanylate cyclase

Motion of proximal histidine and structural allosteric transition in soluble guanylate cyclase

Heme Sensor Proteins

Molecular Mechanisms of Actions for CO

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