Three-dimensional molecular models of neutrophil elastase, proteinase 3, and cathepsin G. The basis for modeling is described in “Materials and methods.” Residues with positively charged side chains are indicated by blue; those with negatively charged side chains are indicated by red. Neutrophil elastase and cathepsin G are modeled with an inhibitor in the active site (orange). The putative glycosaminoglycan-binding regions around the active sites of the enzymes are encircled (yellow). (A-D) Murine neutrophil elastase, (E-F) murine cathepsin G, (I-L) murine proteinase 3. For each protein model, 4 different views separated by sequential 90-degree clockwise rotations around the vertical axis are shown.