Crystal Structure of the Alkylsulfatase AtsK:  Insights into the Catalytic Mechanism of the Fe(II) α-Ketoglutarate-Dependent Dioxygenase Superfamily^†,‡

The alkylsulfatase AtsK from Pseudomonas putida S-313 belongs to the widespread and versatile non-heme iron(II) α-ketoglutarate-dependent dioxygenase superfamily and catalyzes the oxygenolytic cleavage of a variety of different alkyl sulfate esters to the corresponding aldehyde and sulfate. The enzyme is only expressed under sulfur starvation conditions, providing a selective advantage for bacterial growth in soils and rhizosphere. Here we describe the crystal structure of AtsK in the apo form and in three complexes:  with the cosubstrate α-ketoglutarate, with α-ketoglutarate and iron, and finally with α-ketoglutarate, iron, and an alkyl sulfate ester used as substrate in catalytic studies. The overall fold of the enzyme is closely related to that of the taurine/α-ketoglutarate dioxygenase TauD and is similar to the fold observed for other members of the enzyme superfamily. From comparison of these structures with the crystal structure of AtsK and its complexes, we propose a general mechanism for the catalytic cycle of the α-ketoglutarate-dependent dioxygenase superfamily.