Structural basis for cyclodextrin recognition by Thermoactinomyces vulgaris cyclo/maltodextrin-binding proteinTonozuka, T., Sogawa, A., Yamada, M., Matsumoto, N., Yoshida, H., Kamitori, S., Ichikawa, K., Mizuno, M., Nishikawa, A., Sakano, Y.
(2007) FEBS J 274: 2109-2120
- PubMed: 17371546
- DOI: https://doi.org/10.1111/j.1742-4658.2007.05753.x
- Primary Citation of Related Structures:
- PubMed Abstract:
The crystal structure of a Thermoactinomyces vulgaris cyclo/maltodextrin-binding protein (TvuCMBP) complexed with gamma-cyclodextrin has been determined. Like Escherichia coli maltodextrin-binding protein (EcoMBP) and other bacterial sugar-binding proteins, TvuCMBP consists of two domains, an N- and a C-domain, both of which are composed of a central beta-sheet surrounded by alpha-helices; the domains are joined by a hinge region containing three segments. gamma-Cyclodextrin is located at a cleft formed by the two domains. A common functional conformational change has been reported in this protein family, which involves switching from an open form to a sugar-transporter bindable form, designated a closed form. The TvuCMBP-gamma-cyclodextrin complex structurally resembles the closed form of EcoMBP, indicating that TvuCMBP complexed with gamma-cyclodextrin adopts the closed form. The fluorescence measurements also showed that the affinities of TvuCMBP for cyclodextrins were almost equal to those for maltooligosaccharides. Despite having similar folds, the sugar-binding site of the N-domain part of TvuCMBP and other bacterial sugar-binding proteins are strikingly different. In TvuCMBP, the side-chain of Leu59 protrudes from the N-domain part into the sugar-binding cleft and orients toward the central cavity of gamma-cyclodextrin, thus Leu59 appears to play the key role in binding. The cleft of the sugar-binding site of TvuCMBP is also wider than that of EcoMBP. These findings suggest that the sugar-binding site of the N-domain part and the wide cleft are critical in determining the specificity of TvuCMBP for gamma-cyclodextrin.
Department of Applied Biological Science, Tokyo University of Agriculture and Technology, Japan. firstname.lastname@example.org