Leucine is an hydrophobic amino acid and lysine is a basic amino acid. Most of the time, disruption of the normal structure of a protein can occur if the two amino acids substituted have different properties eg chemical properties. Hydrophobic substances normally cluster up within buried sites preventing contact with the fluidic environment while some charged ones are found at the surfaces. Thus substition of leaving which is a hydrophobic amino acid for lysine, a basic amino acid will cause distruption of the normally cluster up buried regions.
