Figure 3.

Hydrogen bond network in the active site of rkbPAP. The hydrogen bond pattern demonstrates how the initial, pre-catalytic enzyme-substrate complex may be stabilized. The protonation state of sulfate at the pH of crystallization (pH 4.0) is SO42-. Residue His295 (indicated by a "*") is the only amino acid that is not invariant among PAPs from different sources.

Schenk et al. BMC Structural Biology 2008 8:6   doi:10.1186/1472-6807-8-6
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