PMID:15337456
| Citation |
Spiwok, V, Lipovová, P, Skálová, T, Buchtelová, E, Hasek, J and Králová, B (2004) Role of CH/pi interactions in substrate binding by Escherichia coli beta-galactosidase. Carbohydr. Res. 339:2275-80 |
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| Abstract |
Interactions between carbohydrates and aromatic amino-acid residues are often observed in structures of carbohydrate-protein complexes. They are characterized by an orientation of the pyranose or furanose ring parallel with the aromatic ring of amino-acid residues. An important role in the formation of these complexes is supposed to be played by CH/pi interactions. This paper presents an ab initio quantum chemistry study of CH/pi interactions between beta-galactosidase from E. coli and its substrates and products. The energy stabilizing the interaction between Trp999 residue and substrate bound in the shallow binding mode was calculated at the MP2/6-31+G(d) level as 5.2kcalmol(-1) for the glucose moiety of allolactose, 2.4kcalmol(-1) for the galactose moiety of allolactose and 5.0kcalmol(-1) for the glucose moiety of lactose. The energy stabilizing the interaction between Trp568 residue and galactose in the deep binding mode was calculated as 2.7kcalmol(-1). Interaction energies at the HF/6-31+G(d) and B3LYP/6-31+G(d) levels were small or repulsive; therefore, highly correlated ab initio methods were necessary to study these interactions. These unexpectedly strong interactions give a rationale for allolactose formation and illustrate the role of the Trp999 residue. In addition, this illustrates the importance of CH/pi interactions for the function of carbohydrate-binding proteins and carbohydrate-processing enzymes. |
| Links |
PubMed Online version:10.1016/j.carres.2004.06.016 |
| Keywords |
Binding Sites; Calorimetry; Carbon; Escherichia coli/enzymology; Escherichia coli Proteins/metabolism; Hexoses/chemistry; Hexoses/metabolism; Hydrogen; Substrate Specificity; Thermodynamics; beta-Galactosidase/metabolism |
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