Conformational analysis and aqueous hydration studies of model peptides for the adhesive protein of the mussel,Mytilus edulis L

Conformations of model peptides of the adhesive protein of the mussel, Mytilus edulis L were investigated using molecular mechanics. The protein structure was represented as the repeat of a 10-residue unit. This decamer, and di- and tri-decamers of it, were considered in the modeling. Incorporation of the unusual dopamine residue in the decamer repeat may be explained by its hydrogen bond forming ability via its 3-OH group to a proline carbonyl oxygen. This bond contributes to maintaining a double reverse β-turn structure in the decamer. This conformation was found more stable than 3₁ and α helical conformations. Adjacent reverse β-turn structures are connected by short segments (2 to 3 residues) having little conformational preference. Thus, the overall protein can possess a significant random nature, yet have a highly ordered embedded conformational component. Hydrophilic character is in line with the larger number of OH groups on the phenyl ring for residue 9 (the site of the Dopa residue). The dehydration free energy of the (3-OH)-Phe as compared to the Dopa derivative is less by 1.4kcal per decamer unit. This amounts to more than 100kcal energy gain in the dehydration process for the total protein.