Fig. 1

Crystal structure of probable p-nitrophenyl phosphatase from Archaeoglobus fulgidus (AfPase, PDB 4jdp). Cartoon representations of the structure of the fold with close-up of different active site configurations. Beta strands are colored dark gray, while alpha-helices are colored light gray. a Side view of AfPase. It shows the Rossmann-like fold of the HAD superfamily and reveals the typical spatial orientations of the conserved residues involved in catalysis. b Close-up active site view of AfPase with motif I–IV signatures. Motif I: conserved amino-acid sequence of DxDx, Motif II: conserved amino-acid of Thr or Ser, Motif III: conserved amino acid of Arg or Lys, Motif IV: conserved amino-acid sequence of (G/S)(D/S)x_2–6(D/N)