FIGURE 1.

Crystal structure of the CTRC-eglin c complex. A, structural overview of the complex. CTRC is shown in blue, with catalytic triad residues Ser¹⁹⁵, His⁵⁷, and Asp¹⁰² in red and disulfide links in yellow. Eglin c is displayed in green. B, view into the substrate binding cleft of CTRC. CTRC is shown with a semitransparent gray surface. Eglin c binding loop residues 40–50 are rendered in stick representation, filling (from left to right) CTRC S₆-S₁ and S₁′-S₅′ subsites. C, retained activation peptide of CTRC. Residues 1–10 of the chymotrypsin C activation peptide are tethered to the activated enzyme through a disulfide link between Cys¹ and Cys¹²². The activation peptide is depicted in cyan in stick representation, with a 2F_o − F_c electron density map contoured at 1.6σ. Strong density around the Leu¹⁰ carboxyl terminus confirms that residues 11–13 of the activation peptide are not disordered but have been proteolytically removed.