Involved in the high-affinity D-xylose membrane transport system. Binds with high affinity to xylose. E.coli has two D-xylose transport systems that accumulate sugar against a concentration gradient: the XylE system which utilizes the electrochemical gradient of protons and that is insensitive to cold osmotic shock and the XylF system that uses a high-energy phosphate compound and is sensitive to cold osmotic shock. Belongs to the bacterial solute-binding protein 2 family.