Crystal structures of beta-amylase from Bacillus cereus var mycoides in complexes with substrate analogs and affinity-labeling reagents. 
The crystal structures of beta-amylase from Bacillus cereus var.  mycoides in complexes with five inhibitors were solved.  The inhibitors used were three substrate analogs, i.e. glucose, maltose (product), and a synthesized compound, O-alpha-D-glucopyranosyl-(1-->4)-O-alpha-D-glucopyranosyl-(1-->4)-D-xylopyranose (GGX), and two affinity-labeling reagents with an epoxy alkyl group at the reducing end of glucose.  For all inhibitors, one molecule was bound at the active site cleft and the non-reducing end glucose of the four inhibitors except GGX was located at subsite 1, accompanied by a large conformational change of the flexible loop (residues 93-97), which covered the bound inhibitor.  In addition, another molecule of maltose or GGX was bound about 30 A away from the active site.  A large movement of residues 330 and 331 around subsite 3 was also observed upon the binding of GGX at subsites 3 to 5.  Two affinity-labeling reagents, alpha-EPG and alpha-EBG, were covalently bound to a catalytic residue (Glu-172).  A substrate recognition mechanism for the beta-amylase was discussed based on the modes of binding of these inhibitors in the active site cleft.