The multicomponent enzyme system of sMMO from Methylococcus capsulatus (Bath) consists of a hydroxylase (MMOH, pdb reference 1MTY), an oxidoreductase (MMOR; consisting of FAD domain, 1TVC, and [2Fe2S]-Fd domain, 1JQ4), and a regulatory (binding) protein (MMOB, 1CKV). The ribbon diagram representation of MMOH is based on X-ray coordinates and those of MMOB and the two truncated MMOR fragments, on NMR structures.