Figure 3.

Division of the titratable groups in Bacillus licheniformis α-amylase. Side chains are shown only for titratable groups. The three active-site residues Asp 231, Glu 261, and Asp 328 (BLA numbering) are colored red. The orange spheres represent inorganic ions present in the X-ray structure. Groups colored yellow are the additional residues that constitute the full subset when E_cutoff is 2.0 kT/e. Additional titratable groups that are included in the full subset when E_cutoff is lowered to 1.0 kT/e are colored magenta. The cyan groups are included when E_cutoff is lowered to 0.5 kT/e. Groups that always are in the nonessential set are colored gray.