Figure 3
The Ca2+-binding site Ca1-2 is degenerated in the C-terminal domain of the P. polymyxa neutral protease Gentlyase. (a) The double calcium site Ca1-2 is occupied by only one Ca2+ in both structures of P. polymyxa neutral protease. Water molecules coordinating the Ca2+ ion (yellow) are shown as red spheres. (b) Ca1-2 in the prototypic neutral protease thermolysin from B. thermoproteolyticus (PDB entry 3fvp ). (c) Superimposition of Ca1-2 in P. polymyxa neutral protease (yellow) with that of thermolysin from B. thermoproteolyticus (green) shows that the Asp185 coordinating the first Ca2+ in thermolysin is substituted by two water molecules and that Lys172 provides the missing positive charge of the second Ca2+ in P. polymyxa neutral protease. Waters were omitted for clarity.  [article HTML]