TABLE 4.
Water-mediated hydrogen bonds at the interface of the rShPI-1/K13L·PPE complex
PPE residues are numbered according to their similar topology with chymotrypsinogen. Numbers in parentheses refer to donor-acceptor distances (Å). Water molecules (W) are labeled according to the numbers in the PDB file, in which they are assigned to the enzyme (e) or inhibitor (i) chains. The suffix “A” indicates amino acid insertions in the PPE sequence compared to that of chymotrypsinogen. The following parameters were used to identify an H-bond: maximal donor-acceptor distance, 3.50 Å; maximal hydrogen-acceptor distance, 2.50 Å; maximal angular errors, 90.00.
| Position | K13L·PPE |
|---|---|
| Å | |
| P4 | Gly10i O--W65i (3.05) |
| W65i--Arg217Ae (3.22) | |
| Gly10i O--W304e (2.84) | |
| W304e--Gln192e OE1 (2.84) | |
| P3 | Arg11i NH1--W72i (2.86) |
| W72i--Asp97e OD1 (3.03) | |
| W72i--Ala99AeN (3.06) | |
| W72i--W59i (3.68)--Val99eN (3.05) | |
| P2′ | Tyr15i OH--W66i (2.69) |
| W66i--Gln150e OE1 (2.99) | |
| W66i--Gly149eO (2.77) | |
| Tyr15i OH--W358e (3.28) | |
| W358e--Leu151eN (2.89) | |
| 2nd loop | Ile32i O--W60i (2.88)--W315e (3.67) |
| W315e--Gln192e NH1 (2.87) | |
| Gly35i O--W293e (2.74) | |
| W293e--Thr96e OG1 (2.60) | |
| Gly37i N--W295e (3.43) | |
| W295e--Thr96e OG1 (2.61) |