Characterization of functional heme domains from soluble guanylate cyclase

Biochemistry. 2005 Dec 13;44(49):16266-74. doi: 10.1021/bi051601b.


Soluble guanylate cyclase (sGC) is a heterodimeric, nitric oxide (NO)-sensing hemoprotein composed of two subunits, alpha1 and beta1. NO binds to the heme cofactor in the beta1 subunit, forming a five-coordinate NO complex that activates the enzyme several hundred-fold. In this paper, the heme domain has been localized to the N-terminal 194 residues of the beta1 subunit. This fragment represents the smallest construct of the beta1 subunit that retains the ligand-binding characteristics of the native enzyme, namely, tight affinity for NO and no observable binding of O(2). A functional heme domain from the rat beta2 subunit has been localized to the first 217 amino acids beta2(1-217). These proteins are approximately 40% identical to the rat beta1 heme domain and form five-coordinate, low-spin NO complexes and six-coordinate, low-spin CO complexes. Similar to sGC, these constructs have a weak Fe-His stretch [208 and 207 cm(-)(1) for beta1(1-194) and beta2(1-217), respectively]. beta2(1-217) forms a CO complex that is very similar to sGC and has a high nu(CO) stretching frequency at 1994 cm(-)(1). The autoxidation rate of beta1(1-194) was 0.073/min, while the beta2(1-217) was substantially more stable in the ferrous form with an autoxidation rate of 0.003/min at 37 degrees C. This paper has identified and characterized the minimum functional ligand-binding heme domain derived from sGC, providing key details toward a comprehensive characterization.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Guanylate Cyclase / chemistry*
  • Guanylate Cyclase / genetics
  • Guanylate Cyclase / metabolism
  • Heme / chemistry*
  • Heme / genetics
  • Heme / metabolism
  • Humans
  • Models, Molecular
  • Molecular Sequence Data
  • Nitric Oxide / metabolism
  • Oxidation-Reduction
  • Protein Conformation*
  • Protein Subunits / chemistry
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Rats
  • Sequence Alignment
  • Solubility
  • Spectrum Analysis, Raman


  • Protein Subunits
  • Nitric Oxide
  • Heme
  • Guanylate Cyclase