FIGURE 4.

IcaB_Ad has a narrow active site pocket compared with PgaB^43–309. A, superposition of IcaB_Ad^{23–280Δloop} (blue) and PgaB^43–309 (orange) shows a strong conservation of the CE4 fold with a root mean square deviation of 1.7 Å over 219 equivalent Cα atoms. β-Hairpin loops for IcaB_Ad are labeled βH1–3, and the Zn²⁺ ion is shown as a sphere colored dark gray. Surface representation of IcaB_Ad^{23–280Δloop} (B) and PgaB^43–309 (C) is shown in the same representation as panel A with residues contributing to the difference in active site architecture colored magenta and green for IcaB_Ad^{23–280Δloop} and PgaB^43–309, respectively. The Ni²⁺ ion in PgaB is shown as a teal-colored sphere.