| - | 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.
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| - | Structural basis for cyclodextrin recognition by Thermoactinomyces vulgaris cyclo/maltodextrin-binding protein., Tonozuka T, Sogawa A, Yamada M, Matsumoto N, Yoshida H, Kamitori S, Ichikawa K, Mizuno M, Nishikawa A, Sakano Y, FEBS J. 2007 Apr;274(8):2109-20. Epub 2007 Mar 20. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=17371546 17371546]
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