tailieunhanh - Báo cáo khoa học: X-ray structure of glucose/galactose receptor from Salmonella typhimurium in complex with the physiological ligand, (2R)-glyceryl-b-D-galactopyranoside

The R-type lectin EW29, isolated from the earthwormLumbricus terrestris, consists of two homologous domains (14 500 Da) showing 27% identity with each other. The C-terminal domain (Ch; C-half) of EW29 (EW29Ch) has two sugar-binding sites in subdomainsaandc, and the protein uses these sugar-binding sites for its function as a single-domain-type hemagglu-tinin. | ễFEBS Journal X-ray structure of glucose galactose receptor from Salmonella typhimurium in complex with the physiological ligand 2R -glyceryl-b-D-galactopyranoside Sanjeewani Sooriyaarachchi1 Wimal Ubhayasekera1 Winfried Boos2 and Sherry L. Mowbray1 1 Department of Molecular Biology Swedish University of AgriculturalSciences Uppsala Sweden 2 Department of Biology University of Konstanz Germany Keywords galactose uptake glucose galactose-binding protein glyceryl galactoside lactose uptake Salmonella enterica serovar Typhimurium Correspondence S. L. Mowbray Department of Molecular Biology Swedish University of Agricultural Sciences Box 590 BiomedicalCenter SE-751 24 Uppsala Sweden Fax 46 18 53 6971 Tel 46 18 471 4990 E-mail mowbray@ Website http Received 13 December 2008 revised 31 January 2009 accepted 2 February 2009 doi 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 typhimurium protein bound to the physiologically relevant ligand 2R -glyceryl-P-D-galactopyranoside solved by molecular replacement and refined to A resolution with R and R-free values of 17 and 22 . The structure identifies three amino acid residues that are diagnostic of 2R -glyceryl-P-D-galactopyranoside binding Thr110 Asp154 and Gln261 as opposed to binding to the monosaccharides glucose and galactose. These three residues are conserved in essentially all available glucose galactose-binding protein sequences indicating that the binding of 2R -glyceryl-P-D-galactopyranoside is the rule rather than the exception for receptors of this type. The role of 2R -glyceryl-P-D-galactopyranoside in bacterial biology is discussed. Further comparison of the available structures provides the .

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