Aromatic side-chain interactions in proteins. Near- and far-sequence His-X pairs.
Several studies have analysed aromatic interactions, involving mostly phenylalanine, tyrosine and tryptophan. Only a few studies have considered histidine as an interacting aromatic residue. An extensive analysis of aromatic His-X interactions is performed here on a data set of 593 PDB structures: 68% of the histidine are involved in aromatic pairs and 1271 non-redundant His-X pairs were analysed. Thirty percent of these pairs involve an aromatic partner less than 6 apart in the sequence. These near-sequence pairs correspond to conformations which stabilise secondary structures, mainly alpha-helices when the residues are 4 apart and beta-strands when they are 2 apart in the sequence. The partners of the other His-X pairs (887, 70%) are more than 5 apart in the sequence. Of these far-sequence pairs, 35% bridge beta strands and only 9% helices. The near-sequence pairs are sterically constrained as supported by conformer distribution. The X partners of far-sequence His-X pairs are mainly "above" the histidine ring with tilted and normal rings, corresponding to a "T shape; face to edge" orientation. Phenylalanine, the only aromatic residue with no heteroatom, is a disfavoured partner, whereas histidine is the preferred one. Heteroatom-heteroatom interactions are favoured in near-sequence as well as in far-sequence His-His, His-Trp and His-Tyr pairs.
Meurisse
Rita
R
Centre de Biophysique Moléculaire Numérique (CBMN), 2, Passage des déportés, Faculté Scientifique Agronomique de Gembloux (FSAGx), Gembloux 5030, Belgium.
Brasseur
Robert
R
Thomas
Annick
A
D024322:Amino Acids, Aromatic / Q000737:chemistry*; D030562:Databases, Protein; D006639:Histidine / Q000737:chemistry*; D008956:Models, Chemical; D010649:Phenylalanine / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*
D024322:Amino Acids, Aromatic; D011506:Proteins; D010649:Phenylalanine; D006639:Histidine