A and B, the chemical shift changes of oryctin between the free state and the bound state to α-chymotrypsin (A) and leukocyte elastase (B). Asterisks represent unassigned residues. C and D, mapping of the chemical shift-perturbed residues on the oryctin molecule by binding to α-chymotrypsin (C) and leukocyte elastase (D). The bars in (A and B) and the residues in (C and D) are colored according to the extent of chemical shift change defined by the formula, δΔ = (δΔHN2 + 0.25 δΔ15N2)1/2 (10). White, 0–0.02 ppm; yellow, 0.02–0.04 ppm; orange, 0.04–0.06 ppm; and red, >0.06 ppm.