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Research article - Peer-reviewed, 2009

X-ray structure of glucose/galactose receptor from Salmonella typhimurium in complex with the physiological ligand, (2R)-glyceryl-beta-d-galactopyranoside

Sooriyaarachchi, Sanjeewani; Ubhayasekera, Wimal; Boos, Winfried; Mowbray, Sherry


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-beta-d-galactopyranoside, solved by molecular replacement, and refined to 1.87 angstrom resolution with R and R-free values of 17% and 22%. The structure identifies three amino acid residues that are diagnostic of (2R)-glyceryl-beta-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-beta-d-galactopyranoside is the rule rather than the exception for receptors of this type. The role of (2R)-glyceryl-beta-d-galactopyranoside in bacterial biology is discussed. Further, comparison of the available structures provides the most complete description of the conformational changes of glucose/galactose-binding protein to date. The structures follow a smooth and continuous path from the most closed structure [that bound to (2R)-glyceryl-beta-d-galactopyranoside] to the most open (an apo structure).


galactose uptake; glucose; galactose-binding protein; glyceryl galactoside; lactose uptake; Salmonella enterica serovar Typhimurium

Published in

FEBS Journal
2009, volume: 276, number: 7, pages: 2116-2124

Authors' information

Sooriyaarachchi, Sanjeewani
Swedish University of Agricultural Sciences, Department of Molecular Biology
Ubhayasekera, Wimal
Swedish University of Agricultural Sciences, Department of Molecular Biology
Boos, Winfried
University of Konstanz
Mowbray, Sherry
Swedish University of Agricultural Sciences, Department of Molecular Biology

UKÄ Subject classification

Biochemistry and Molecular Biology

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