Amino-aromatic interactions in proteins

Abstract

Geometric analysis of 33 refined high-resolution protein crystal structures (2 Å or higher) demonstrates that side-chain amino groups interact with aromatic side chains. Positively charged or δ(+) amino groups of lysine, arginine, asparagine, glutamine and histidine are preferentially located within 6 Å of the ring centroids of phenylalanine, tyrosine and trytophan, where they make van der Waals' contact with the δ(-) π-electrons and avoid the δ(+) ring edge. This geometric pattern is different from the distribution expected due to random close packing of side chains in a protein. It is opposite to oxygen- and sulfur-aromatic interactions, similar to aromatic-aromatic interactions, and almost certainly electrostatic in origin. © 1986.