Summary for clan CO

Summary Structure Literature
HistoryMEROPS 8.3 (22 December 2008)
DescriptionCysteine nucleophile; catalytic residues in the order Cys, His, His in sequence
Contents of clanClan CO contains a single family of cysteine exopeptidases, C40.
Evidence (see Protein fold)
Catalytic mechanism(See family C40.)
Peptidase activity(See family C40.)
Protein foldAll 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.


Family Family Type Peptidase Structure
C40 dipeptidyl-peptidase VI (bacteria) (Lysinibacillus sphaericus) Yes

Distribution of clan CO among Kingdoms of Organisms