D CTRC Ser214 (Ser236) (Fig. 2C). The Leu45 carbonyl oxygen is positioned to interact with the CTRC oxyanion hole amide nitrogens of Ser195 (Ser216) and Gly193 (Gly214). Around the primed side, added Hbonds are formed among P2 residue Leu47 and CTRC Thr41 (Thr58) (Fig. 2C). The S1 key specificity pocket of CTRC, occupied inside the complicated by the side chain of eglin c Leu45, is shaped by the hydrophobic side chains of CTRC residues Ala190 (Ala211), Val213 (Val235), and Val226 (Val250) (Fig. 2C). A far more shallow hydrophobic depression within the substrate binding cleft is shaped by the side chains of CTRC Leu99 (Leu118) and Phe215 (Phe237), which form a binding pocket for P4 residue Pro42. Around the primed side, the S2 subsite, a pocket bordered by the fundamental side chain of CTRC Arg143 (Arg162) plus the hydrophobic side chain of Ile151 (Ile169), is filled by the hydrophobic P2 residue Leu47 (Fig. 2C). The backbone conformation of eglin c residues 4349 bound to CTRC closely parallels that observed within the previously reported structure of eglin c with bovine chymotrypsin (PDB 1ACB (22)). By contrast, eglin c residues 39 42 are shifted compared together with the bovine chymotrypsineglin c complex to lie three further removed from a standard patch formed by CTRC residues Arg175 (Arg195), Arg218 (Arg241), and Lys224 (Lys248) (Fig. 2D). This basic pocket types the S6 subsite of CTRC, which is occupied within the complex by a coordinated phosphate ion inside the absence of a side chain around the eglin c P6 residue Gly40 (Fig. 2D). Structural Insights into CTRC Substrate SpecificityCTRC has been shown to act as a regulator of pancreatic zymogen activation by targeting a precise set of substrate cleavage internet sites not recognized by other chymotrypsin or elastaselike digestive proteases (Table 1) (five, six, 15, 16). 1 element of this specificity is much more extremely effective cleavage following Leu residues when compared with other chymotrypsin and elastase isoforms (16). By contrast, the elastase isoforms show broad P1 specificity but comparatively low catalytic efficiency on brief peptide substrates, whereas chymotrypsins prefer aromatic residues Phe, Tyr, or Trp at P1 (16). The position occupied in CTRC by Val226 (Val250), one of many hydrophobic residues shaping the S1 pocket (Fig.Boc-Ser-OtBu Order 2C), is in other chymotrypsins filled by Gly or Ala, and theVOLUME 288 Quantity 14 APRIL 5,FIGURE 1.Methyl 5-bromo-7-azaindole-6-carboxylate uses Crystal structure of your CTRCeglin c complex.PMID:23996047 A, structural overview from the complicated. 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 in to the substrate binding cleft of CTRC. CTRC is shown using a semitransparent gray surface. Eglin c binding loop residues 40 0 are rendered in stick representation, filling (from left to right) CTRC S6S1 and S1 S5 subsites. C, retained activation peptide of CTRC. Residues 10 of the chymotrypsin C activation peptide are tethered towards the activated enzyme through a disulfide hyperlink between Cys1 and Cys122. The activation peptide is depicted in cyan in stick representation, having a 2Fo Fc electron density map contoured at 1.six . Strong density around the Leu10 carboxyl terminus confirms that residues 113 from the activation peptide are usually not disordered but happen to be proteolytically removed.9852 JOURNAL OF BIOLOGICAL CHEMISTRYStructure of the CTRCEglin c ComplexFIGURE 2. Eglin c inhibitory interaction with CTRC. A, stabilization of your inhibitory loop of eglin c. The eglin c binding loop assumes a su.
