Albany 2015:Book of Abstracts

Albany 2015
Conversation 19
June 9-13 2015
©Adenine Press (2012)

Ion-π interactions in biomolecular systems

Aromatic groups are ubiquitous in all domains of chemistry and biology. Lately, the interest for non-covalent interactions involving ions and aromatic groups such as cation- π and, more recently, anion-π interactions, increased significantly. Cation-π interactions were found to play essential roles in proteins. On the other hand and despite the abundance of aromatic groups in nucleic acids, no convincing examples of cation-π involving nucleobases were found. Instead, early crystal structures of tRNA molecules showed that phosphate groups form close contacts with the aromatic plane of uridines suggesting that nucleobases could be involved in anion-π rather than cation-π interactions (Figure).

In order to understand this counter-intuitive behavior of aromatic groups, we calculated electrostatic potential (ESP) maps for aromatic amino acids and nucleobases that support the fact that the latter are not suited to form cation-π interactions. A survey of the Protein Data Bank (PDB) revealed that these anion-π interactions occur essentially in RNA systems where they take the form of phosphate-π interactions and are recurrently found in tetraloop motifs such as the tRNA anticodon and T- loops among others. Since tetraloops are ubiquitous in the RNA world, phosphate-π interactions appear as an significant member of the ensemble of non-covalent interactions structuring biomolecular systems. Such interactions have therefore to be considered in modeling undertakings such as in silico RNA folding and molecular dynamics simulation techniques.


Luigi D'Ascenzo
Pascal Auffinger

Architecture et Reactivite de l'ARN
Universite de Strasbourg
Institut de Biologie Moleculaire et Cellulaire du CNRS
Strasbourg, 67084, France