Figure 3. Hydrogen-bonding networks in the active sites of (A) wild-type PBP 5, (B) PBP 5-G105D (PBP 5′) and (C) Cys¹¹⁵ (2ME)-modified PBP 5, shown as stereo representations with important residues in bond form.

Potential hydrogen bonds are shown as dashed lines. In comparison with the views of wild-type and G105D mutant PBP 5, the Cys¹¹⁵ modification in the 2ME-modified enzyme has caused Ser¹¹⁰ to be displaced away from the active site and, as a result, its hydrogen bond with Lys²¹³ is lost and Lys²¹³ now contacts Ser⁴⁴. Note also the altered position of Lys⁴⁷ in the modified enzyme, which now contacts the carbonyl of Ser¹¹⁰ instead of His¹⁵¹. This Figure was prepared using PYMOL (pymol.sourceforge.net).