Quaternary structure controls ligand dynamics in soluble guanylate cyclase.
Soluble guanylate cyclase (sGC) is the mammalian endogenous nitric oxide (NO) receptor. The mechanisms of activation and deactivation of this heterodimeric enzyme are unknown. For deciphering them, functional domains can be overexpressed. We have probed the dynamics of the diatomic ligands NO and CO within the isolated heme domain β(1)(190) of human sGC by piconanosecond absorption spectroscopy. After photo-excitation of nitrosylated sGC, only NO geminate rebinding occurs in 7.5 ps. In β(1)(190), both photo-dissociation of 5c-NO and photo-oxidation occur, contrary to sGC, followed by NO rebinding (7 ps) and back-reduction (230 ps and 2 ns). In full-length sGC, CO geminate rebinding to the heme does not occur. In contrast, CO geminately rebinds to β(1)(190) with fast multiphasic process (35, 171, and 18 ns). We measured the bimolecular association rates 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). These different dynamics reflect conformational changes and less proximal constraints in the isolated heme domain with respect to the dimeric native sGC. We concluded that the α-subunit and the β(1)(191-619) domain exert structural strains on the heme domain. These strains are likely involved in the transmission of the energy and relaxation toward the activated state after Fe(2+)-His bond breaking. This also reveals the heme domain plasticity modulated by the associated domains and subunit.
Laboratoire d'Optique et Biosciences, INSERM U696, CNRS UMR 7645 Ecole Polytechnique, 91128 Palaiseau, France.
Byung-Kuk
BK
Yoo
Isabelle
I
Lamarre
Jean-Louis
JL
Martin
Michel
M
Negrerie
D000494:Allosteric Regulation; D000818:Animals; D002248:Carbon Monoxide / Q000737:chemistry / Q000378:metabolism; D002417:Cattle; D006162:Guanylate Cyclase / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000737:chemistry; D006801:Humans; D008024:Ligands; D008027:Light; D008168:Lung / Q000201:enzymology; D009569:Nitric Oxide / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism*; D000071756:Soluble Guanylyl Cyclase; D013329:Structure-Activity Relationship
D008024:Ligands; D018160:Receptors, Cytoplasmic and Nuclear; D009569:Nitric Oxide; D006418:Heme; D002248:Carbon Monoxide; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase