Characterization of two different five-coordinate soluble guanylate cyclase ferrous-nitrosyl complexes

Biochemistry. 2008 Mar 25;47(12):3892-9. doi: 10.1021/bi7022943. Epub 2008 Feb 27.


Soluble guanylate cyclase (sGC), a hemoprotein, is the primary nitric oxide (NO) receptor in higher eukaryotes. The binding of NO to sGC leads to the formation of a five-coordinate ferrous-nitrosyl complex and a several hundred-fold increase in cGMP synthesis. NO activation of sGC is influenced by GTP and the allosteric activators YC-1 and BAY 41-2272. Electron paramagnetic resonance (EPR) spectroscopy shows that the spectrum of the sGC ferrous-nitrosyl complex shifts in the presence of YC-1, BAY 41-2272, or GTP in the presence of excess NO relative to the heme. These molecules shift the EPR signal from one characterized by g 1 = 2.083, g 2 = 2.036, and g 3 = 2.012 to a signal characterized by g 1 = 2.106, g 2 = 2.029, and g 3 = 2.010. The truncated heme domain constructs beta1(1-194) and beta2(1-217) were compared to the full-length enzyme. The EPR spectrum of the beta2(1-217)-NO complex is characterized by g 1 = 2.106, g 2 = 2.025, and g 3 = 2.010, indicating the protein is a good model for the sGC-NO complex in the presence of the activators, while the spectrum of the beta1(1-194)-NO complex resembles the EPR spectrum of sGC in the absence of the activators. Low-temperature resonance Raman spectra of the beta1(1-194)-NO and beta2(1-217)-NO complexes show that the Fe-NO stretching vibration of the beta2(1-217)-NO complex (535 cm (-1)) is significantly different from that of the beta1(1-194)-NO complex (527 cm (-1)). This shows that sGC can adopt different five-coordinate ferrous nitrosyl conformations and suggests that the Fe-NO conformation characterized by this unique EPR signal and Fe-NO stretching vibration represents a highly active sGC state.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Allosteric Regulation
  • Animals
  • Computer Simulation
  • Electron Spin Resonance Spectroscopy
  • Ferrous Compounds / chemistry*
  • Guanosine Triphosphate / chemistry
  • Guanylate Cyclase / chemistry*
  • Heme / chemistry
  • Nitric Oxide / chemistry*
  • Rats
  • Solubility
  • Spectrum Analysis, Raman


  • Ferrous Compounds
  • Nitric Oxide
  • Heme
  • Guanosine Triphosphate
  • Guanylate Cyclase