Solved the 1.68 A crystal structure of Variovorax paradoxus S110 IadC (PDB 7YLR), revealing a Class IA FMN-type reductase with an FMN-binding domain (residues 1-115), an NADH-binding domain (residues 116-238), and a plant-type [2Fe-2S] cluster domain (residues 239-329) coordinated by four cysteines.
"The overall triangle-shaped protein is composed of 3 major domains, including an FMN-binding domain (FBD, residues 1–115), an NADH-binding domain (NBD, residues 116–238), and a plant-type [2Fe-2S] cluster domain (FeSD, residues 239–329) (Fig 4C)."
Demonstrated that IadC transfers electrons from NADH via FMN and its [2Fe-2S] cluster to IadD/IadE to catalyze IAA conversion to oxIAA, and that mutations in FMN-binding residues or the [2Fe-2S] ligand Cys279 impair IAA turnover.
"FMN is thought to mediate electron transfer from the NADH electron donor to the [2Fe-2S] electron acceptor, which further delivers the electrons to the dioxygenase for the catalysis reaction [29,30] (Fig 4C and 4E). As anticipated, mutation of residues involved in FMN binding compromised IAA turnover (Fig 4D). Similarly, the C279S mutation impairing coordination of the [2Fe-2S] cluster significantly decreased the efficiency of the reaction."