Two views of the Cα trace of PGABN rotated 90° relative to one another about a horizontal axis. The zinc ion is shown as a grey sphere. Surface loops near the active site are shown in blue. These regions are presumably flexible in solution and have no counterpart in SlCE4 or PdaA. They may bind to PgaA in the periplasm. Residues 195–200 are not visible in the electron-density map for the copy of the molecule shown.