Part of the ABC transporter complex ModABC involved in the transport of molybdenum into the cell (Probable). Binds tungstate and molybdate (PubMed:31627455, PubMed:25172858). Can also bind chromate, with lower affinity (PubMed:31627455). Plays an essential role in recruitment of molybdate for nitrate reduction (PubMed:25172858). The complex is composed of two ATP-binding proteins (ModC), two transmembrane proteins (ModB) and a solute-binding protein (ModA). Deletion of the gene reduces cellular molybdate concentrations and results in inhibition of anaerobic growth and nitrate reduction. Belongs to the bacterial solute-binding protein ModA family.