HIS 92 THR 93 GLY 7 HR 91 USER 8 SP 76 LASN /cYs 6 The above centrally-placed water molecule makes strong hydrogen bonds to residues in three separated parts of he ribonuclease molecule holding them together. this water molecule and its binding site are conserved across the entire family of microbial ribonucleasesThe above centrally-placed water molecule makes strong hydrogen bonds to residues in three separated parts of the ribonuclease molecule holding them together. This water molecule and its binding site are conserved across the entire family of microbial ribonucleases