Summary for clan CO
| History | MEROPS 8.3 (22 December 2008) |
| Description | Cysteine nucleophile; catalytic residues in the order Cys, His, His in sequence |
| Contents of clan | Clan CO contains a single family of cysteine exopeptidases, C40. |
| Evidence | (see Protein fold) |
| Catalytic mechanism | (See family C40.) |
| Peptidase activity | (See family C40.) |
| Protein fold | All solved tertiary structures reminiscent of the papain fold, with two subdomains, one consisting of a helical bundle and which bears the catalytic Cys, the other a beta barrel bearing the other active site residues (Aramini et al., 2008). Unlike papain, where the catalytic Cys is at the N-terminus of a helix, in the structures from family C40 the active site Cys is at the C-terminus of a helix, which means the sequence must run in the opposite direction to that in papain. No similarity between the structures can be detected using the DALI algorithm (Holm & Sander, 1995). The structural resemblances are therefore assumed to be derived from convergent rather than divergent evolution, and proteins in C40 are assigned to the clan CO. |
Families
| C40 |
dipeptidyl-peptidase VI (bacteria) (Lysinibacillus sphaericus) |
Yes |
Distribution of clan CO among Kingdoms of Organisms
