SUGAR Binding

Fig. 10. Mechanisms of steady-slqte kinetics of sugar phosphorylation catalyzed by E-IIs in a non-compartmentalized system. (A) The R. sphaeroides 11 model. The model is based on the kinetic data discussed in the text. Only one kinetic route leads to phosphorylation of fructose. (B) The E. coli ll " model. The model in Fig. 8 was translated into a kinetic scheme that would describe mannitol phosphorylation catalyzed by Il solubilized in detergent. Two kinetic routes lead to phosphorylation of mannitol. Mannitol can bind either to state EPcy, or EPpe,. E represents the complex of SF (soluble factor) and 11 and II in A and B, respectively. EP represents the phosphorylated states of the E-IIs. Subscripts cyt and per denote the orientation of the sugar binding site to the cytoplasm and periplasm, respectively. PEP, phosphoenolpyruvate.

Fig. 2. The simple asymmetric carrier model for glucose transport. C denotes a sugar-binding site, which can exist in an outward-facing (Co) or an inward-facing (Ci) conformation. Dissociation constants for sugar binding are bja and ejf. Rate constants for carrier re-orientation are c, d, g, and h.

Because the rates of sugar binding to and dissociation from the transporter are very rapid compared to the rates of transporter re-orientation, the Michaelis constants for transport by the simple asymmetric carrier model are given by the following equations,... 

Using these equations, Lowe and Walmsley [48] have calculated the dissociation constants for sugar binding at the extracellular surface of the membrane (K s = b a in Fig. 2) and at the cytoplasmic surface (K. = elf = bid) x [dgich]) from the estimated rate constants for carrier re-orientation and the measured Michaelis constants. The dissociation constant for binding at the extracellular surface of the membrane, calculated in this way, is approximately lOmM and is largely unaffec-... 

Lager, I., Looger, L. L., Hilpert, M., Lalonde, S. and Frommer, W. B. (2006). Conversion of a putative Agrobacterium sugar-binding protein into a FRET sensor with high selectivity for sucrose. J. Biol. Chem. 281, 30875-83. 

Identify sugar-binding proteins involved in pathogenicity... 

Our initial parametrization of the LIE equation was subsequently used for HIV protease and trypsin inhibitors as well as in a study of sugar binding to a bacterial receptor protein. While it was at first suspected that a... 

Table I. Amino acid residues considered in modelling the sugar binding site of ConA (including the two metal ions)...

In a recent study, Hamodrakas et al. (25) using proton NMR measurements and a sophisticated interactive graphics facility proposed two possible modes of binding for 4 -nitrophenyl a-D-mannopyranoside to ConA. These two orientations differ from the two favoured orientations for aMeMan proposed in the present study. These authors fitted the ligand in the sugar binding site... 

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