Interactions of carbohydrates with biomolecules. Role of the CH/pi interactions
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| Year of publication | 2013 |
| Type | Conference abstract |
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| Description | Molecular recognition plays crucial role in many biological processes, such as bacteria-host identification. Some of these recognition processes are performed by proteins called lectins, which are able to bind saccharides in a very specific way. In our study we have focused on RSL lectin from world-wide distributed bacteria Ralstonia solanacearum causing lethal wilt in many agricultural crops and the AAL lectin from Aleuria aurantia. Both above mentioned bacteria interact with hosts through their lectins, binding predominantly L-fucose. In this paper, we are interested in the role of the CH/pi interaction in binding abilities of these two lectins. In the RSL lectin, we have attempted for the first time to quantify how the CH/pi interaction contributes to a overall carbohydrate - protein interaction. We have used an experimental approach, creating single and double point mutants, combined with high level computational methods. The structure contains three monomer units of the lectin with six almost identical binding sites, where three of them are intramonomeric and the other three are intermonomeric. Experimentally measured binding affinities were compared with computed carbohydrate-aromatic acid residue interaction energies. Experimental binding affinities for the RSL wild type, phenylalanine and alanine mutants were -8.5, -7.1 and -4.1 kcal.mol-1, respectively. These affinities agree with the computed dispersion interaction energy between the carbohydrate and aromatic amino acid residues for RSL the wild type and the phenylalanine mutant, with respective values of -8.8 and -7.9 kcal.mol-1, excluding the alanine mutant where the interaction energy was -0.9 kcal.mol-1. Molecular dynamics simulations show that discrepancy can be caused by creation of a new hydrogen bond between the alpha-L-Me-fucoside and RSL. Observed results suggest that in this and similar cases the carbohydrate-receptor interaction can be driven mainly by a dispersion interaction. |
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