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. Author manuscript; available in PMC: 2011 Jul 1.
Published in final edited form as: Arch Biochem Biophys. 2010 Sep 18;505(1):13–21. doi: 10.1016/j.abb.2010.09.012

Figure 5.

Figure 5

A close-up view of the actives sites of (A) HppE in complex with 2-HPP, (B) HEPD in complex with 2-HEP, and (C) DhpI in complex with 2-HEP. Despite the lack of any notable sequence similarities, both HEPD and HppE use a near identical constellation of active site residues to carry out their respective reactions. Notably, both polypeptides contain composite active sites with a catalytically essential lysine residue (colored in cyan) from a different subunit interacting with the active site. A comparison of HppE, HEPD, and DhpI co-crystal structures illustrates the chemical features that are used by functionally and structurally distinct enzymes to harbor phosphonate substrates.