Before revision:  Except for this very important salt bridge, other three important salt bridges GLU196--ARG156--HIS187 and GLU211--HIS177 are also found to greatly contribute to the structural stability of horse prion protein.
After revision:  Except for this very important salt bridge, other three important salt bridges GLU196-ARG156-HIS187, ARG156-ASP202 and GLU211-HIS177 are also found to greatly contribute to the structural stability of horse prion protein.