Part of the ABC transporter complex FusABC-MsmK involved in short- and long-chain fructooligosaccharide (FOS) import. Required for the utilization of long-chain FOSs (PubMed:23264576). Binds kestose, nystose, fructofuranosyl-nystose and inulin, but not sucrose. Has a preference for long-chain FOSs (tetrasaccharides and larger) (PubMed:27939783). The complex is composed of two ATP-binding proteins (MsmK), two transmembrane proteins (FusB and FusC) and a solute-binding protein (FusA). The calcium-binding site is essential for the translocation of fructooligosaccharide (FOS) substrates by the transporter. Belongs to the bacterial solute-binding protein 1 family.