C-terminal catalytic domain of the oxygenase alpha subunit of naphthalene 1,2-dioxygenase (NDO) and related aromatic ring hydroxylating dioxygenases
C-terminal catalytic domain of the oxygenase alpha subunit of naphthalene 1,2-dioxygenase (NDO) and related Rieske-type non-heme iron aromatic ring-hydroxylating oxygenases (RHOs, also known as aromatic ring hydroxylating dioxygenases). This domain binds non-heme Fe(II). RHOs utilize non-heme Fe(II) to catalyze the addition of hydroxyl groups to the aromatic ring, an initial step in the oxidative degradation of aromatic compounds. RHOs are composed of either two or three protein components, and are comprised of an electron transport chain (ETC) and an oxygenase. The ETC transfers reducing equivalents form the electron donor to the oxygenase component, which in turn transfers electrons to the oxygen molecules. The oxygenase components are oligomers, either (alpha)n or (alpha)n(beta)n. The alpha subunits are the catalytic components and have an N-terminal domain, which binds a Rieske-like 2Fe-2S cluster, and a C-terminal domain which binds the non-heme Fe(II). The Fe(II) is co-ordinated by conserved His and Asp residues. Proteins belonging to this subgroup include the terminal oxygenase alpha subunits of biphenyl dioxygenase, cumene dioxygenase from Pseudomonas fluorescens IP01, ethylbenzene dioxygenase, naphthalene 1,2-dioxygenase, nitrobenzene dioxygenase from Comamonas sp. strain JS765, toluene 2,3-dioxygenase from Pseudomonas putida F1, dioxin dioxygenase of Sphingomonas sp. Strain RW1, and the polycyclic aromatic hydrocarbons (PAHs)degrading ring-hydroxylating dioxygenase from Sphingomonas CHY-1. This subfamily belongs to the SRPBCC (START/RHO_alpha_C/PITP/Bet_v1/CoxG/CalC) domain superfamily of proteins that bind hydrophobic ligands. SRPBCC domains have a deep hydrophobic ligand-binding pocket.