Dicamba Monooxygenase: Structural Insights into a Dynamic Rieske Oxygenase that Catalyzes an Exocyclic Monooxygenation

Structural Features in the KshA Terminal Oxygenase Protein That Determine Substrate Preference of 3-Ketosteroid 9 -Hydroxylase Enzymes

“…Dicamba monooxygenase (PDB accession number 3GKE) shows the highest structural similarity (3D) with KshA of M. tuberculosis (www.rcsb.org). On the basis of an analysis of the crystal structures of dicamba monooxygenase, D'Ordine et al (4) suggested that entry of the substrate into the active site is enabled by movement of a helix region and a loop region, resulting in a more open or closed state of the active site. Characterization of the KshA chimeric proteins in the present study thus provides the first experimental evidence that the loop present at the entrance of the active site strongly affects the substrate preference of KSH enzymes.…”

“…Several three-dimensional (3D) structures of ROs are currently available (3,4,6,7,8,9,13,15,17,19,20), including a single 3D structure of KshA, namely, that of M. tuberculosis H37Rv (Rv3526; KshA H37Rv ) (2). Although the protein sequences of ROs vary considerably, their tertiary structures are very similar overall.…”

“…Characteristic for ROs, including KshA H37Rv , is the formation of trimers. These trimers either occur as ␣3 subunits (2,4,17,19) or may additionally include a smaller ␤ subunit of the oxygenase component, resulting in an (␣␤)3 enzyme complex (3,6,7,8,9,13,15,20). The active site of KshA H37Rv was shown to be composed of a ␤ sheet, including a loop region located at the entrance of the active site, flanked by two ␣ helices.…”

Evolutionary Changes in Chlorophyllide a Oxygenase (CAO) Structure Contribute to the Acquisition of a New Light-harvesting Complex in Micromonas*

“…Co-immunoprecipitation and BN-PAGE followed by immunoblotting showed that the MpCAO1 and MpCAO2 proteins form a heterodimer. As far as we know, the Rieske-mononuclear iron oxygenase forms a homotrimer of c3 symmetry (45)(46)(47). The Micromonas CAO may be the first example of a Rieske-mononuclear iron oxygenase that forms a heterodimer.…”

Structural and Molecular Genetic Analyses of the Bacterial Carbazole Degradation System

“…31) The crystal structures of the trimeric oxygenase components of RO have been reported for the terminal oxygenase components of 2-oxoquinoline 8-monooxygenase 33) and dicamba monooxygenase. 34,35) The overall shapes of these trimeric oxygenases are highly homologous to that of CARDO-O J3 , although that of 2-oxoquinoline 8-monooxygenase has an additional small C-terminal trimerization domain consisting of one helix that forms the contacts in the center of the trimer. Based on these crystal structures, the doughnut-like or ring-like structure is likely to be common to the terminal oxygenase components of an 3 configuration.…”