Part of the tripartite ATP-independent periplasmic (TRAP) transport system YiaMNO involved in the uptake of 2,3-diketo-L-gulonate. The complex comprises the extracytoplasmic solute receptor protein YiaO, and the two transmembrane proteins YiaM and YiaN. Belongs to the TRAP transporter large permease family. Was originally proposed to be a subunit from an L-xylulose uptake system, but PubMed:16385129 shows that it does not bind L- or D-xylulose.