Salt-Tolerant Structure Features of Mussel Adhesive Proteins

Mussel adhesive proteins have strong salt-tolerant adhesion ability and can assist marine mussels to firmly fix themselves on underwater structures. In our previous study, the adhesion ability of mussel adhesive proteins was largely attributed to the pair structure of Tyr/Dopa with basic residues (i.e., Lys and Arg) rather than the post-translational modification of Tyr to Dopa. However, the mechanism underlying the protein maintaining its adhesion ability at high salt concentrations remains unknown. In this work, we use all-atom molecular dynamics simulation to investigate the structure of mussel adhesive protein Pvfp-5β-Tyr in a salt solution. The responses of the residue pairs composed of Tyr and basic residues to elevated salt concentrations are discussed. We noticed that the residue pairs are mostly bound by anions rather than cations. The bound anions induce an electrostatic screening effect that hinders further anion binding. Furthermore, the residue pairs can resist the disruption from bound anions on the inter-residue interactions. Thus, such a pair structure is largely retained for the protein in the solution with high salt concentration. Taken together, our simulations reveal that the imbalanced anion binding and robust residue pair structure should be responsible for the salt-tolerant adhesion ability of mussel adhesive proteins.