Secondary structure topologies for the Acel_2062 protein and other metallopeptidases. Helices are shown as red barrels, strands are shown as pink arrows and connecting regions of random coil and turns are shown as thin blue arrows. “N” and “C” indicate the N- and C-terminus. Numbers indicate the residue range of each structural element. The positions of the zinc ligands and catalytic Glu are indicated by the letters “H”, “D” and “E”. Some images have been rotated and/or flipped to that these active site residues are in equivalent positions. Key to structures: 3E11[PDB:3e11], mini- zincin, Acidothermus cellulolyticus; 4JIU[PDB:4jiu], mini-Glu-zincin, Pyrococcus abyssi; 3LMC[PDB:3lmc], archaelysin, Methanocorpusculum labreanum; 1KUH[PDB:1kuh], snapalysin, Streptomyces caespitosus; 2EJQ[PDB:2ejq], mini- zincin, Thermus thermophilus; 1AST[PDB:1ast], astacin, Astacus astacus.