Fig. 1.

Models for NO activation of sGC. In the scheme depicted in black, NO binds rapidly to the basally active five-coordinate ferrous heme, forming a six-coordinate ferrous-nitrosyl intermediate. At a rate that depends on NO concentration, the final five-coordinate complex is activated several hundred-fold. In the scheme depicted in red, the modulation of the formation and dissociation of the sGC heme-NO complex is shown, as well as the activation state of ferrous-nitrosyl sGC, by ATP, GTP, and NO.