Signal discrimination analyses based on the domain structure of soluble guanylate cyclase

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We have revealed that there were two kinds of nucleotide binding sites, a catalytic and a pseudo-nucleotide sites in soluble guanylate cyclase. When carbon monoxide combined to the enzymic heme, the binding of YC-1 to the pseudo-nucleotide binding site increased the affinity of a nucleotide for the pseudo nucleotide binding site, through interaction between two binding sites. Furthermore, we have first confirmed the formation of the oxygenated form of the enzyme, which was stable under frozen conditions. The formation of the oxygenated form was noted to be regulated by YC-1 binding, and also was suggested to be governed by the deformation of the heme iron from the heme plane, based on the EXAFS analyses.