Mammalian soluble Guanylate Cyclase (sGC), working as a physiological NO receptor, is investigated using resonance Raman spectroscopy for NO bound states with different saturation levels in the presence and absence of effectors. The Fe–NO (νFe–NO) and N–O (νN-O) stretching bands appeared at 521 and 1681 cm-1, respectively, without effectors, but νN-O was split into 1681 and 1699 cm-1 in the presence of GTP and shifted to 1687 cm-1 in the presence of YC-1 or BAY 41-2272, while νFe-NO remained unaltered. The split two νN-O bands were independent of NO saturation levels. GTP or YC-1/BAY 41-2272 altered the vinyl and propionate bending modes from 423 to 399 cm-1 and 376 to 367 cm-1, respectively. Based on these observations, allosteric effects on NO …protein interactions are discussed.
