Adsorption Behavior and Mechanism of SCA-1 on a Calcite Surface: A Molecular Dynamics Study

The crystallization mechanism for natural mineral, especially the role of biological molecules in biomineralization, is still under debate. Protein adsorption on material surfaces plays a key role in biomineralization. In this article, molecular dynamics (MD) simulations were performed to systematically investigate the adsorption behavior of struthio camelus eggshell protein struthiocalcin-1 (SCA-1) on the calcite (104) surface with several different starting orientations in an explicit water environment. For each binding configuration, detailed adsorption behaviors and a mechanism were presented with the analysis of interaction energy, binding residues, hydrogen bonding, and structures (such as DSSP, dipole moment, and the electrostatic potential calculation). The results indicate that the positively charged and polar residues are the dominant residues for protein adsorption on the calcite (104) surface, and the strong electrostatic interaction drives the binding of model protein to the surface. The hydrogen bond bridge was found to play an important role in surface interactions as well. These results also demonstrate that SCA-1 is relatively rigid in spite of strong adsorption with few structural changes in α-helix and β-sheet contents. The results of the orientation calculation suggest that the dipole moment of the protein tends to remain parallel to calcite in most stable cases, which was confirmed by electrostatic potential isosurfaces analysis.