We also explored the relationship between conserved interaction networks and the active site architecture (Figure ). Each residue was classified as "Catalytic" (directly involved in catalysis), "Active Site" (within 5 Å of a co-crystalised transition state analogue, see Figure ) and "Other" (all other residues). . Because we are interested in polar interactions that might vary with mutation, we filtered the interactions to only include those that were non-hydrophobic and involved at least one side-chain residue. This decision was based on the observations made from Both our analysis on the crystal structure and MD simulation datasets highlights E166 (which acts as a general base in class A β-lactamase catalysis ( )) to be one of the residues with the highest per residue conservation score. This is primarily as a result of the highly conserved hydrogen bonds E166 forms with the side-chains of residues S70, N136 and N170, and the salt bridge with K73. Taken together, this would suggest these interactions with E166 are essential for class A β-lactamase catalysis, which is consistent with the literature on class A ß-lactamases . However, only the MD-based network is able to identify conserved interactions for the second catalytically important residue, S70. This residue is responsible for the formation of a covalent acyl intermediate during the catalytic reaction . MD simulations sampled alternative S70 conformations that were not observed in available crystal structures. Subsequent KIN analysis identified conserved hydrogen bonds between S70 -K73 and S70 -E166. These interactions are consistent with the established role of S70 in facilitating proton transfer between K73 and E166 (50; 51). Additionally, Figure illustrates that analysis of MD trajectories gave more insight into highly conserved interactions concentrated around the active site. The MD-based network identifies conserved interactions involving 78% of the active site residues, while the crystallographic network identifies only 41%. Furthermore, 40% of the MD-identified residues are contained within the top 20% of the KIN per-residue scores. These conserved interactions within the active site region form a hydrogen-bonding network. These observations demonstrate that KIN can serve as a useful complimentary tool for characterizing evolutionarily conserved active site interactions.