There are several ways how saccharides may interact with their receptors (e.g. classical hydrogen bonds, through metal ions as Ca(II)). The CH/π interactions that occur between carbohydrates and aromatic amino-acids are also strongly involved in carbohydrate-recognition process. The strength and importance of the CH/π carbohydrate-aromatic interaction is recently under heavy discussion among biomolecular scientists. Some of a recognition processes are performed by proteins called lectins, which are able to bind saccharides in a very specific way.
In case of the RSL lectin, we have attempted for the first time to quantify how the CH/π interaction contributes to an overall carbohydrate - protein interaction. We have used an experimental approach, creating single and double point mutants, combined with high level computational methods. Experimentally measured binding affinities were compared with computed carbohydrate-aromatic acid residue interaction energies.
The AAL lectin is fucose-specific lectin with five structurally different binding sited for fucose moiety. Additionally, it has been discovered, that the AAL N224Q mutant structure exhibits interesting conformational flipping of incident Trp residue in two of the three binding sites that contain Trp side-chain. We aim to discover the nature of this Trp-flipping in mentioned binding sites. Therefore, we have attempted to analyze the impact of dispersion interaction to total binding potency also for AAL.
Observed results suggest that in this and similar cases the carbohydrate-receptor interaction can be driven mainly by a dispersion interaction.
This work was funded by the European Community’s Seventh Framework Programme under the European Regional Development Fund (CZ.1.05/1.1.00/02.0068) and Capacities specific programme (286154). The project is supported within the SoMoPro programme (project No. 2SGA2747, co-funded by FP7/2007-2013 under grant agreement No. 229603). The research is also co-funded by the South Moravian region. The authors thank the Czech National Supercomputing Centre, METACENTRUM, for providing computational resources (research intent LM2010005).
