title: Histidine hydrogen bonding in MHC at pH 5 and pH 7 modeled by molecular docking and molecular dynamics simulations.
abstract: Hydrogen bonds play important roles in maintaining the structure of proteins and in the formation of most biomolecular protein-ligand complexes. All amino acids can act as hydrogen bond donors and acceptors. Among amino acids, Histidine is unique, as it can exist in neutral or positively charged forms within the physiological pH range of 5.0 to 7.0. Histidine can thus interact with other aromatic residues as well as forming hydrogen bonds with polar and charged residues. The ability of His to exchange a proton lies at the heart of many important functional biomolecular interactions, including immunological ones. By using molecular docking and molecular dynamics simulation, we examine the influence of His protonation/deprotonation on peptide binding affinity to MHC class II proteins from locus HLA-DP. Peptide-MHC interaction underlies the adaptive cellular immune response, upon which the next generation of commercially-important vaccines will depend. Consistent with experiment, we find that peptides containing protonated His residues bind better to HLA-DP proteins than those with unprotonated His. Enhanced binding at pH 5.0 is due, in part, to additional hydrogen bonds formed between peptide His(+) and DP proteins. In acidic endosomes, protein His(79β) is predominantly protonated. As a result, the peptide binding cleft narrows in the vicinity of His(79β), which stabilizes the peptide - HLA-DP protein complex.
authors.forename: Atanas
authors.initials: A
authors.lastname: Patronov
authors.forename: Edvokiya
authors.initials: E
authors.lastname: Salamanova
authors.forename: Ivan
authors.initials: I
authors.lastname: Dimitrov
authors.forename: Darren R
authors.initials: DR
authors.lastname: Flower
authors.affiliation: Faculty of Pharmacy, Medical University of Sofia, 2 Dunav st., 1000 Sofia, Bulgaria. idoytchinova@pharmfac.net.
authors.forename: Irini
authors.initials: I
authors.lastname: Doytchinova
mesh_terms: D003198:Computer Simulation; D005802:Genes, MHC Class II; D006682:HLA-DP Antigens / Q000737:chemistry / Q000378:metabolism; D006639:Histidine / Q000737:chemistry*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular
chemical_list: D006682:HLA-DP Antigens; D006639:Histidine