Sugar-binding site

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.

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... 

It seems reasonable to conclude from these studies that if mutarotase and the sugar-binding site in intestine and the red blood cell are not identical at least they are structurally very similar. 

Fig. 16. A schematic drawing of the hexokinase dimer showing the location of observed glucose and nucleotide binding sites. The two sugar binding sites are represented by 5 and S. The intersubunit AMP-PNP site I is formed by regions Iu and Id of each subunit. The symmetry related sites are indicated by Iu and Id. The location of the AMP binding sites in the monomeric Bill crystal form are labeled A and A. From Anderson et at. (72).

Equilibrium-dialysis studies showed two equivalent, sugar-binding sites on each isolectin intrinsic association-constants (Ka ) were 1450 230 M l for binding to D-mannose and 773 126 M I to methyl a-D-glucopyranoside. 453... 

Stiiegler S, Tewes E (2002) Investigation of sugar-binding sites in ternary hgand-copper(II)-carbohydrate complexes. Eur J Inorg Chem 2 487... 

Ahramson. J., Smirnova, I.. Kasho, V.. Verner. O., Iwata. S., and Kaback, H. R. 200J. The lactose permease of Escherichia cnii Overall structure, the sugar-binding site and the alternating access mndel lor transport. FEBS Lett.. 55.5 96-101. 

We will use the example of concanavalin A, abundant in jack bean flour. Final purification is done by absorption on a Sephadex column from which the lectin is eluted by a glucose solution. Concanavalin A is formed from four subunits— MW = 26 500 daltons—associated in dimers below pH 5.6 and tetramers above. Each subunit contains Mn, Ca, and a sugar binding site. Figure 15.2 shows their mode of association, with the location of the ions and the binding site. A very important part of polypeptide chains are j8-sheets. These are the regions where the associations between monomers take place. 

CBM Family 13 adopt the p-trefoil fold first encountered with the ricin B (carbohydrate-binding) chain. It contains 12 strands of p-sheet arranged in such a way as to provide three independent sugar binding sites with different specificities, and again binding is enthalpy driven. 

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