Figure 3 ppnP proteins have conserved pocket (A-D ) Electrostatics surface representation of the ppnP structures. The potential substrate-binding pocket is indicated by yellow dash lines. (E ) Residues composed of the pocket of Ec ppnP are shown as the stick. (F ) Sequence alignment of Ec ppnP,Pa ppnP, St ppnP, and Vc ppnP, and Yersinia pestis ppnP. The residues involved in dimerization are indicated by black squares. And the residues composed of the potential pocket are indicated by red circles.