Arrangement of the superimposed S1 binding pockets and water molecules of (A) AST-Free (red), BT-Free (blue), and BT-K15G with the main chain of the BPTI residues 14–16 (green); (B) AST-1BZA (red), BT-ANL (blue), and BT-1BZA (green); (C) AST-2BEA (red), BT-2BEA (blue), BT-FBA (green), and BT-AMC (magenta); (D) AST-3PEA (red), BT-3PEA (blue), and *BT-3PEA (1TNJ; green); (E) AST-4PPA (red) and *BT-4PPA (1TNK; green); and (F) BT-5PBA (blue) and *BT-5PBA (1TNI; green). The structures with an asterisk (*) are from Kurinov and Harrison (1994).