Involved in iodate respiration (PubMed:34215855). May accept electrons from cytochrome c551, and catalyze the reduction of iodate (IO(3)(-)) to produce the chemically unstable intermediate hypoiodous acid (HIO). This intermediate then undergoes abiotic disproportionation to yield two molecules of iodide (I(-)) and one molecule of iodate. The resultant iodate subsequently cycles back into the reductive pathway (PubMed:34215855). The initial reduction of iodate may inadvertently produce low levels of incidental toxic H(2)O(2), which is detoxified by IdrP1 and IdrP2 (PubMed:34215855). Binds 1 [3Fe-4S] cluster per subunit. Binds 1 molybdenum-bis(molybdopterin guanine dinucleotide) (Mo-bis-MGD) cofactor per subunit. The iodate reductase (Idr) complex is composed of a molybdopterin-dependent iodate reductase (IdrA and IdrB subunits) and two associated peroxidases (IdrP1 and IdrP2). May be co-transported with IdrB into the periplasm. Deletion mutant is incapable of growth via iodate respiration, while growth under oxic conditions remains unimpaired. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.