The open and closed conformations of the cleft giving access to the active site are observed in the same crystal structure. The side-chains of the residues of the two mobile loops are shown, as well as the side-chain of the essential catalytic residue: Glu19 located in the depth of the cleft, at the C-terminal end of the first helix.
In this simulation, only the two extreme conformations are experimental and scientifically significative. All the intermediate images are only a simulation without scientific meaning.