Crystallization and structural analysis of intact maltotetraose-forming exo-amylase from Pseudomonas stutzeri.

The intact maltotetraose-forming exo-amylase from Pseudomonas stutzeri (G4-1), which has a raw starch binding domain, has been crystallized. The structure was identified (PDB entry 1GCY) by the molecular replacement method using the structure of its catalytic domain (G4-2). The result showed that the raw starch binding domain is in a disordered state, the corresponding electron densities being almost invisible. Superposition of these two enzyme forms showed evidence for the possible location of the raw starch binding domain (SBD). This crystal is a novel case, in that it forms a regular lattice incorporating flexibly bound SBD in the channel of crystal packing of the catalytic domains.