Structure of proline 3‐hydroxylase

Iron (II)/2‐oxoglutarate (2‐OG)‐dependent oxygenases catalyse oxidative reactions in a range of metabolic processes including the hydroxylation of proline and lysine residues during the post‐translational modification of collagen. 2‐OG oxygenases commonly require ascorbate for full activity. In the vitamin C deficient disease, scurvy, reduced activity of 2‐OG oxygenases results in impaired formation of collagen. Here we report the crystal structure of bacterial proline 3‐hydroxylase from Streptomyces sp., an enzyme which hydroxylates proline at position 3, the first of a 2‐OG oxygenase catalysing oxidation of a free α‐amino acid. Structures were obtained for the enzyme in the absence of iron (to 2.3Å resolution, R=20.2%, Rfree=25.3%) and that complexed to iron (II) (to 2.4Å resolution, R=19.8%, Rfree=22.6%). The structure contains conserved motifs present in other 2‐OG oxygenases including a ‘jelly roll’β strand core and residues binding iron and 2‐oxoglutarate, consistent with divergent evolution within the extended family. The structure differs significantly from many other 2‐OG oxygenases in possessing a discrete C‐terminal helical domain. Analysis of the structure suggests a model for proline binding and a mechanism for uncoupling of proline and 2‐OG turnover.