Part of the ABC transporter complex ModABC involved in the transport of molybdenum into the cell (PubMed:8576221). Binds molybdate with high affinity in vitro and with a similar affinity in vivo (PubMed:21861186, PubMed:28150901, PubMed:9545596, PubMed:8576221, PubMed:21784948, PubMed:8409926). Binds tungstate with high affinity in vitro (PubMed:28150901, PubMed:9545596, PubMed:8576221, PubMed:21784948). Binds unnatural anion perrhenate with high affinity in vitro (PubMed:21861186). Does not bind sulfate, phosphate, arsenate, selenate, chlorate, metavanadate, nitrate, perchlorate, permanganate or carbonate (PubMed:9545596, PubMed:28150901, PubMed:8576221). The complex is composed of two ATP-binding proteins (ModC), two transmembrane proteins (ModB) and a solute-binding protein (ModA). Expression is up-regulated by molybdate limitation (PubMed:7860583). Repressed by molybdate-bound ModE (PubMed:8550508). Cells are unable to transport molybdate unless high levels of it is supplied in the culture medium. May be useful in radiopharmaceutical applications as an engineered disulfide bond-containing protein with increased affinity for perrhenate (PubMed:21861186). May be used to remove chromate, which is toxic to many biological systems, from environmental aqueous solutions (PubMed:28150901). Belongs to the bacterial solute-binding protein ModA family. According to a report, does not bind chromate (PubMed:8576221). According to another report, binds chromate with high affinity and is able to remove it from an aqueous solution in vitro (PubMed:28150901). The mod operon containing this protein has previously been called the chlD locus.