Resonance raman investigation of effects of YC-1 and GTP on structure of CO-bound heme of soluble guanylate cyclase

Resonance Raman (RR) spectra of soluble guanylate cyclase (sGC) reported by five independent research groups have been categorized into two types; sGC1 and sGC2. Here we demonstrate that the RR spectra of sGC isolated from bovine lung contains only sGC2 while both species are observed in the spectra of CO-bound form (CO-sGC). The relative populations of the two forms altered from an initial composition in which the CO-sGC2 form predominated, with the Fe-CO (νFe-CO) and C-O stretching modes (νCO) at 472 and 1985 cm-1, respectively, to a composition dominated by the CO-sGC1 form with νFe-CO and νCO at 488 and 1969 cm-1, following the addition of xenobiotic, YC-1. Further addition of a substrate, GTP, completed the change. GDP and cGMP had a similar but significantly smaller effect, while a substrate analogue, GTP-γ-S had an effect similar to that of GTP. In contrast, ATP had a reverse effect, and suppressed the effects of YC-1 and GTP. In the presence of both YC-1 and GTP, vinyl vibrations of heme were significantly influenced.