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Updated: May 26, 2026
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Comparing the Affinity of GTPase-binding Proteins using Competition Assays
Published on: October 8, 2015
Quaternary structure controls ligand dynamics in soluble guanylate cyclase
Byung-Kuk Yoo1, Isabelle Lamarre, Jean-Louis Martin
1Laboratoire d'Optique et Biosciences, INSERM U696, CNRS UMR 7645 Ecole Polytechnique, 91128 Palaiseau, France.
The Journal of Biological Chemistry
|January 7, 2012
Summary
The isolated heme domain of soluble guanylate cyclase (sGC) shows distinct ligand dynamics compared to the full enzyme, revealing insights into sGC activation mechanisms.
Area of Science:
- Biochemistry
- Molecular Biology
- Spectroscopy
Background:
- Soluble guanylate cyclase (sGC) is the primary mammalian receptor for nitric oxide (NO).
- The precise mechanisms governing sGC activation and deactivation remain largely unelucidated.
- Overexpression of functional domains offers a pathway to study enzyme mechanisms.
Purpose of the Study:
- To investigate the dynamics of nitric oxide (NO) and carbon monoxide (CO) ligands within the isolated heme domain (β(1)(190)) of human sGC.
- To compare ligand dynamics in the isolated heme domain with those in full-length sGC.
- To understand the role of structural constraints and conformational changes in sGC function.
Main Methods:
- Piconanosecond absorption spectroscopy was employed to probe ligand dynamics.
- Studies were conducted on both isolated sGC heme domain (β(1)(190)) and full-length sGC.
- Photo-excitation experiments were performed on nitrosylated sGC and its isolated heme domain.
Main Results:
- In isolated β(1)(190), both NO photo-dissociation and photo-oxidation were observed, followed by NO rebinding and back-reduction.
- CO geminate rebinding occurred in the isolated β(1)(190) domain via a multiphasic process (35, 171, and 18 ns).
- In contrast, CO geminate rebinding to the heme was not observed in full-length sGC, and NO geminate rebinding occurred rapidly (7.5 ps).
- Bimolecular association rates (k(on)) differed significantly between sGC and β(1)(190), with k(on) = 0.075 ± 0.01 × 10^6 M⁻¹·S⁻¹ for sGC and 0.83 ± 0.1 × 10^6 M⁻¹·S⁻¹ for β(1)(190).
Conclusions:
- The isolated heme domain exhibits distinct ligand dynamics, including photo-dissociation and oxidation, not seen in full-length sGC.
- The differences in dynamics suggest reduced proximal constraints and conformational flexibility in the isolated heme domain.
- Structural strains exerted by the α-subunit and the β(1)(191-619) domain on the heme domain are crucial for energy transmission and relaxation during activation.
- Heme domain plasticity is modulated by associated domains and subunits, impacting sGC activation pathways.
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