Figure 5

Spatial model of Aca s 4 built by homology modeling and simulations. (a) The Aca s 4 structure (in ribbon representation) is composed of the consensus α-amylase domains A (green), B (red), and C (brown). Three catalytic residues (D196, E232, D297) in the active site are highlighted (orange ball-and-stick). The calcium ion is depicted as a magenta sphere. The chloride binding site (blue sticks) is composed of the conserved binding residues R194 and R334 and the residue S295, which is specific for mite α-amylases; the chloride ion is shown as a light blue sphere. The disulfide bridges are represented by yellow sticks. (b) A superposition of Cα traces of Aca s 4 (magenta) with HPA (cyan; PDB: 2CPU) used as a template for Aca s 4 modeling. The disulfide bridges are represented by yellow (Aca s 4) and orange (HPA) sticks; non-conserved disulfides are marked by asterisks. (c) The surface model of Aca s 4; the right-hand view is in the same orientation as in (a). The molecule is colored red for residues that are identical for Aca s 4 and Der p 4.