Involved in galactan degradation (PubMed:27501980, PubMed:29240795). Part of the ABC transporter complex GanPQS involved in the uptake of galactooligosaccharides (PubMed:27501980, PubMed:29240795). Binds mainly galactotetraose and galactotriose (PubMed:27501980). The complex is composed of two ATP-binding proteins (MsmX), two transmembrane proteins (GanP and GanQ) and a solute-binding protein (GanS). Repressed by the transcriptional regulator GanR and induced by galactobiose. Also repressed by glucose. Deletion mutant displays a 2-fold increase in the doubling time when galactan is the sole carbon and energy source. Belongs to the bacterial solute-binding protein 1 family. Was originally described as a cyclodextrin-binding protein, but it was shown later that it has no affinity for cyclodextrin.