Glucose and galactose receptor

NMR Studies of Fluorinated Sugars Binding to the Glucose and Galactose Receptor... 

J. Aqvist and S. L. Mowbray, Sugar recognition by a glucose/galactose receptor. 

Stable and potent P2Y2 receptor agonists are being administered by inhalation as a potential treatment for cystic fibrosis. P2YH receptors are unusual in that they are activated by UDP-glucose, UDP galactose and UDP-N-acetylglucosamine [22],... 

Figure 1. Sttucture of the E. coli D- glucose and D-galactose receptor. Shown is the (A) a-carbon backbone structure of the receptor with p-D-glucose in the sugar binding pocket and Ca(n) ion in the metal binding site. (B) illustrates the residues that are involved in binding the sugar in the pocket.

Figure 4. F NMR spectra of (A) two-dimensional NOESY exchange of 3 mM 4-fluoro-4-deoxy-galactose and 2 mM receptor at 25°C. Diagonal peaks show the one-dimensional spectrum which is projected on the top of the map. (B) 1.6 mM 4-fluoro-4-deoxy glucose and 0.8 mM receptor at 25°C and (C) 2°C. (D) 1 mM 4-fluoro-4-deoxy-galactose and 2 mM receptor at 2° C.

Luck, L. A., Vance, J. E., O Connell, T. M. and London, R. E. (1996) 19F NMR relaxation studies on 5-fluorotryptophan- and tetradeutero-5-fluorotryptophan-labeled E. coli glucose/ galactose receptor. Journal of Biomolecular NMR, 7, 261-272. 

Schematic representation of glucose (or galactose) transport by the enterocyte. Glucose binds to the receptor, facilitated by the simultaneous binding of two Na+ at separate sites. The glucose and Na" " are released in the cytosol as the receptor affinity for them decreases. The Na" " are actively extruded at the basolateral surface into the intercellular space by Na+,K+-ATPase, which provides the energy for the overall transport. Glucose is transported out of the cell into the intercellular space and thence to portal capillaries, both by a serosal carrier and by diffusion. (Reproduced with permission from G. M. Gray, Carbohydrate Absorption and Malabsorption in Gastrointestinal Physiology. Raven Press,...

Where / is the RTP intensity for a particular concentration of carbohydrate /o is the initial intensity without carbohydrate while /nm is the limiting intensity K is the stability constant of the receptor with guest [C] is the concentration of carbohydrate. The stability constants of BrQBA-carbohydrate complex were obtained as 2.6x103 mol/L for fructose, 1.8xl03 mol/L for galactose, 1.6xl03 mol/L for glucose and 1.3x 103 mol/L for mannose, respectively. 

D-Mannose, D-glucose, and 2-acetamido-2-deoxy-D-glucose have been coupled to albumin to form pseudoglycoproteins for use in a study of receptor-mediated binding of glycoproteins by alveolar macrophages. Fluoresceinyl derivatives of D-mannose, lactose, 2-acetamido-2-deoxy-a-D-galactose, and L-fucose have been covalently attached to albumin and used for direct visualization of membrane lectins in situ. ... 

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