Mammalian sGC is a heterodimer composed of α- and β-subunits (Figure 1). The C-terminus of each subunit contains a catalytic domain and the active site is composed of residues from both subunits. The catalytic domains also form a pseudosymmetric active site that contains residues known to be involved in nucleotide binding, but lack the amino acids required for catalysis. Sequence analysis shows that each subunit also contains well-defined PAS-like domain, and a predicted helical region. The N-termini of the α- and β-subunits are homologous to the H-NOX (H eme-N itric oxide/OX ygen) family of proteins. The N-terminus of β-subunit contains a ferrous heme cofactor that serves a receptor for NO. sGC activity is also modulated by ATP and the substrate GTP and recent studies point toward a more complicated role for NO in the regulation of activity. Structural results coupled with biochemical and cellular experiments have broadened the current molecular view of the regulation of sGC.
Department of Chemistry, University of California
Department of Molecular and Cell Biology, University of California