Family C78


Summary Holotypes Alignment Tree Genomes Structure Literature H-seq M-seq

Summary for family C78

Family type peptidaseC78.001 - UfSP1 peptidase (Mus musculus), MEROPS Accession MER0041174 (peptidase unit: 1-217)
Content of familyPeptidase family C78 contains peptidases that cleave a glycyl bond at the C-terminus of ubiquitin-fold modifier-1 protein.
History Identifier created: MEROPS 7.8 (23 April 2007)
Ubiquitin-fold modifier-1 (Ufm1) is a protein structurally and functionally similar to ubiquitin. Like ubiquitin, Ufm1 can be conjugated to intracellular proteins via a C-terminal glycine. Tagged proteins are not targetted for degradation, and the physiological function is unknown. Ufm1 is synthesized as a precursor and is activated by the removal of a C-terminal dipeptide by peptidases in family C78. These peptidases are also responsible for the release of Ufm1 from conjugates (Kang et al., 2007).
Catalytic typeCysteine
Active site residuesY41 C53 D175 H177 
Active siteThe tertiary structure of UfSP1 (C78.001) shows the catalytic residues to be Cys53 (which has also been identified by labelling with Ufm1-vinylmethylester and by site-directed mutagenesis) and His177. Additional residues shown to be important are Tyr41, which helps form the oxyanion hole, and Asp175, which orientates the imidazolium ring of the active site histidine (Ha et al., 2008). The cysteine occurs within an Asp-Xaa-Gly-Trp-Gly-Cys-Xbb-Tyr-Arg motif where Xaa is any amino acid and Xbb is either Gly or Ala. The aspartate and histidine residues occur within a Xcc-Asp-Pro-His-Xdd-Xaa-Gly motif where Xcc is an aliphatic residue and Xdd is tyrosine or phenylalanine. This motif is very similar to that around the catalytic histidine in family C54, where the aspartate has also been proposed to be the third member of a catalytic triad.
Activities and specificitiesUfSP1 (C78.001) has been shown to process the Ufm1 precursor and to remove Ufm1 from conjugated proteins. UfSP2 (C78.002) can also perform both reactions, but much less efficiently (Kang et al., 2007).
Molecular structureThe tertiary structure has been solved for UfSP1 (C78.001) and shows a papain-like structure (Ha et al., 2008). Hence family C78 is included in clan CA. However, families C54 and C78 are unusual members of the clan in that the third member (Asp in both C54 and C78) of the catalytic triad is N-terminal of the His rather than C-terminal as it is in all other families in the clan. UfSP2 has an additional N-terminal domain of unknown function.
Distribution of family Bacteria -  
Archaea -  
Protozoa details  
Fungi details  
Plants details  
Animals details  
Viruses -  
Biological functionsThe biological significance of the conjugation of proteins with Ufm1 is unknown, but it is assumed to be a signal that is switched when the Ufm1 moiety is removed by UfSP1 or UfSP2.
Statistics for family C78Sequences:897
Identifiers with PDB entries:2
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
UfSP1 peptidaseC78.001Yes
UfSP2 peptidaseC78.002Yes
CG16979 protein (Drosophila melanogaster)C78.A01-
At3g48380 protein (Arabidopsis thaliana)C78.A02-
F38A5.1 protein (Caenorhabditis elegans)C78.A03-
DDB_G0282953 protein (Dictyostelium discoideum)C78.A04-
family C78 non-peptidase homologuesnon-peptidase homologue-
family C78 unassigned peptidasesunassigned-