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![[Figure 4]](wa5073fig4mag.jpg)
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Figure 4
Structural comparisons between Cwp84 and other cysteine proteases. (a) Comparison of cysteine protease propeptides and prosegment binding loops (PBLs). Structures are rendered as coils for simplicity. Overview of the whole region, showing the Cwp84 propeptide in red and cysteine protease domain in green, and the cathepsin K (PDB entry 7pck; cathepsin L-like; Sivaraman et al., 1999  ) propeptide in yellow with the cysteine protease domain in blue; Cwp84 active-site residues are shown in purple. Active-site residues of Cwp84 are shown in magenta and those of cathepsin K are shown in black. Both propeptides cover the active-site groove, shown on the left. Cathepsin propeptides wrap around the protein, interacting with the PBL and forming a conserved helix, while Cwp84 folds back on itself and wraps around the lectin-like domain, leaving the top of the active site considerably more exposed. (b) Cross-eyed three-dimensional view of the PBL. The usually conserved α-helix and short β-sheet are not present in Cwp84, with the whole chain rotated roughly 90°. A turn or short loop below the PBL is replaced by a 16-residue loop that occupies the space normally taken up by the propeptide. (c) Cross-eyed three-dimensional comparison of cysteine protease occluding loop regions. Cwp84 is shown in green, cathepsin L (PDB entry 1cjl; Coulombe et al., 1996) in blue and cathepsin B (PDB entry1pbh; Turk et al., 1996) in olive. The active-site residues of Cwp84 (Gln110, C116A and His262) are shown in purple, those of cathepsin L are shown in black and those of cathepsin B in brown. The fold of cathepsin L is well conserved; many cathepsin L-like proteases will superpose very closely in this region. The relatively short loop does not affect interactions with the active site. Cathepsin B-like proteases have a significantly longer, more variable loop that controls substrate specificity and confers carboxypeptidase activity. The equivalent loop in Cwp84 is closer to that of cathepsin L-like proteases but is slightly longer and could be involved in substrate binding. |
![[Figure 4]](wa5073fig4.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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