Environmental Effects on Salt Bridge Stability in the Protein-Protein Interface: The Case of Hen Egg-White Lysozyme and Its Antibody, HyHEL-10.

Abstract

We studied the stability of two salt bridges between hen egg-white lysozyme (HEL) and its antibody, HyHEL-10, by using molecular dynamics simulations. It was observed that one salt bridge, D32H-K97Y, was stable, whereas the other, D99H-K97Y, was not. To understand this difference, we compared several reduced salt bridge models that incorporated the salt bridges and nearby residues. The results showed the importance of nearby residues, especially Y33H and W98H. Furthermore, to understand the effects of nearby salt bridges, we investigated two mutants, D32HA and D99HA. We found that the D32HA mutation considerably stabilized the D99H-K97Y salt bridge. The reduced model analysis indicated that this can be largely attributed to a conformational change of the main chain.