Periplasmic binding proteins are abundant in bacteria by virtue of their essential roles as high-affinity receptors in ABC transport systems and chemotaxis. One of the best studied of these receptors is the so-called glucose⁄galactose-binding protein. Here, we report the X-ray structure of the Salmonella typhimuriumprotein bound to the physiologically relevant ligand, (2R)-glyceryl-b-d-galactopyranoside, solved by molecular replace-ment, and refined to A˚ resolution with RandR-free values of 17% and 22%
