The crystal structures ofThermoactinomyces vulgariscyclo⁄maltodextrin-binding protein (TvuCMBP) complexed with a-cyclodextrin (a-CD), b-cyclodextrin (b-CD) and maltotetraose (G4) have been determined. A common functional conformational change among all solute-binding pro-teins involves switching from an open form to a closed form, which facili-tates transporter binding.