title: Cation-pi interactions in protein-protein interfaces.
abstract: Arginine is an abundant residue in protein-protein interfaces. The importance of this residue relates to the versatility of its side chain in intermolecular interactions. Different classes of protein-protein interfaces were surveyed for cation-pi interactions. Approximately half of the protein complexes and one-third of the homodimers analyzed were found to contain at least one intermolecular cation-pi pair. Interactions between arginine and tyrosine were found to be the most abundant. The electrostatic interaction energy was calculated to be approximately 3 kcal/mol, on average. A distance-based search of guanidinium:aromatic interactions was also performed using the Macromolecular Structure Database (MSD). This search revealed that half of the guanidinium:aromatic pairs pack in a coplanar manner. Furthermore, it was found that the cationic group of the cation-pi pair is frequently involved in intermolecular hydrogen bonds. In this manner the arginine side chain can participate in multiple interactions, providing a mechanism for inter-protein specificity. Thus, the cation-pi interaction is established as an important contributor to protein-protein interfaces.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal. crowley@itqb.unl.pt
authors.forename: Peter B
authors.initials: PB
authors.lastname: Crowley
authors.forename: Adel
authors.initials: A
authors.lastname: Golovin
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D001665:Binding Sites; D002412:Cations / Q000737:chemistry*; D030562:Databases, Protein; D019281:Dimerization; D006860:Hydrogen Bonding; D008024:Ligands; D011506:Proteins / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D002412:Cations; D008024:Ligands; D011506:Proteins