Aromatic side-chain interactions in proteins. I. Main structural features.
In a data set of 593 nonhomologous proteins from the PDB, we have analyzed the pairing of phenylalanine, tyrosine, tryptophan, and histidine residues with their closest aromatic partner. The frequency distribution of the shortest interatomic distance of partners is bimodal with a sharp peak at approximately 3.8 A and a wider one at a longer distance. Only the 3.8 A peak corresponds to direct ring-ring interactions thus aromatic pairs. The aromatic pairs were separated into two classes, near-sequence pairs and far-sequence pairs. Near sequence pairs stabilize local structure, and far-sequence pairs stabilize tertiary structure. Far-sequence pairs (74% of all pairs) mainly bridge two beta-strands, followed by pairs that bridge a beta-strand and a helix, and pairs that bridge a beta-strand and a random coil structure. Pairs that bridge helices are rare. The secondary structure of the near-sequence pairs depends on the partner distance in the sequence. When the partners are 1, 3, or 4 residues apart in the sequence, pairs are mostly found in helical structures. When the partners are two apart, pairs are mostly found in the same beta-strand. Analysis of the frequency of near sequence pairs supports the hypothesis that aromatic pairing occurs after, rather than before, the formation of secondary structures.
Thomas
Annick
A
Institut National de la Santé et de la Recherche Médicale Unité 410, Paris Cedex, France. thomas.a@fsagx.ac.be
Meurisse
Rita
R
Charloteaux
Benoit
B
Brasseur
Robert
R
D024322:Amino Acids, Aromatic / Q000737:chemistry*; D000818:Animals; D006639:Histidine / Q000737:chemistry; D015394:Molecular Structure; D010649:Phenylalanine / Q000737:chemistry; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D020539:Sequence Analysis, Protein; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
D024322:Amino Acids, Aromatic; D011506:Proteins; D014443:Tyrosine; D010649:Phenylalanine; D006639:Histidine; D014364:Tryptophan