title: Functional hypothesis on miraculin' sweetness by a molecular dynamics approach.
abstract: Miraculin differs from other sweet-tasting proteins because it is a taste-modifier having the unusual property of modifying sourness into sweetness. Its dimer is covalently linked by an inter-chain disulphide bond, and shows its taste-modifying activity at acidic pH, with maximum at pH 3.0, while it is flat at neutral pH. Previous studies suggested the importance of two histidine residues for the taste-modifying activity of miraculin. In this work, we have conducted molecular dynamics simulations on wild type miraculin and on three mutated dimers (H29A, H59A and H29A/H59A) both at neutral and acidic pH to investigate the structural and functional role of these two His residues. Our results suggested that at acidic pH the presence of two charged His at the interface induced a structural rearrangement of the two monomers, thus leading to their relative opening and the following adaptation of their conformation to the receptor surface. On the other hand the simulations on three mutants showed that the mutated dimers had a closed form, and highlighted the important role of H29 in stabilizing/destabilizing the dimer arrangement and also a cooperative effect of the two histidines.
authors.affiliation: Department of Biochemistry and Biophysics, Second University of Naples, via Costantinopoli 16, 80138 Naples, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Paladino
authors.forename: Giovanni
authors.initials: G
authors.lastname: Colonna
authors.forename: Angelo M
authors.initials: AM
authors.lastname: Facchiano
authors.forename: Susan
authors.initials: S
authors.lastname: Costantini
mesh_terms: D001236:Aspergillus oryzae / Q000235:genetics / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009154:Mutation; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D013549:Sweetening Agents / Q000737:chemistry* / Q000494:pharmacology; D013649:Taste / Q000187:drug effects*
chemical_list: D006023:Glycoproteins; D011994:Recombinant Proteins; D013549:Sweetening Agents