InterPro domain: IPR015879

Aromatic ring hydroxylating dioxygenases are multicomponent 1,2-dioxygenase complexes that convert closed-ring structures to non-aromatic cis-diols [ 1 ]. The complex has both hydroxylase and electron transfer components. The hydroxylase component is itself composed of two subunits: an alpha-subunit of about 50kDa, and a beta-subunit of about 20kDa. The electron transfer component is either composed of two subunits: a ferredoxin and a ferredoxin reductase or by a single bifunctional ferredoxin/reductase subunit. Sequence analysis of hydroxylase subunits of ring hydroxylating systems (including toluene, benzene and napthalene 1,2-dioxygenases) suggests they are derived from a common ancestor [ 2 ]. The alpha-subunit binds both a Rieske-like 2Fe-2S cluster and an iron atom: conserved Cys and His residues in the N-terminal region may provide 2Fe-2S ligands, while conserved His and Tyr residues may coordinate the iron. The beta subunit may be responsible for the substrate specificity of the dioxygenase system [ 2 ].

This entry represents the conserved C-terminal domain found in the alpha subunit of aromatic-ring-hydroxylating dioxygenases. It is the catalytic domain of aromatic-ring- hydroxylating dioxygenase systems. The active site contains a non-heme ferrous ion coordinated by three ligands.

1. Nucleotide sequences of the Acinetobacter calcoaceticus benABC genes for benzoate 1,2-dioxygenase reveal evolutionary relationships among multicomponent oxygenases. J. Bacteriol. 173, 5385-95