Jr. Stone et al., ELECTRON-PARAMAGNETIC-RESONANCE SPECTRAL EVIDENCE FOR THE FORMATION OF A PENTACOORDINATE NITROSYL-HEME COMPLEX ON SOLUBLE GUANYLATE-CYCLASE, Biochemical and biophysical research communications, 207(2), 1995, pp. 572-577
Nitric oxide (.NO) is an important intercellular signaling agent throu
ghout the animal kingdom. The majority of the effects of .NO is due to
the direct stimulation of soluble guanylate cyclase (sGC). It has bee
n proposed that .NO activates sGC by interacting with a heme moiety on
the enzyme. The electron paramagnetic resonance (EPR) spectra of the
ferrous-[N-14/N-15] nitrosyl complexes of the purified enzyme have bee
n obtained The spectrum of the [N-14]nitrosyl-sGC complex was almost i
dentical to that of a 5-coordinate nitrosyl-heme model compound, indic
ating that the nitrosyl complex formed on sGC is 5-coordinate. Hyperfi
ne coupling constants and g-values were determined from computer simul
ations of the EPR spectra. Electronic absorption spectroscopy was used
to show that the 5-coordinate nitrosyl complex on sGC forms under con
ditions that are typically used to assay activation of the enzyme. (C)
1995 Academic Press, Inc.