Summary for clan PB
| Clan type peptidase | T01.970 - archaean proteasome, alpha subunit (Thermoplasma acidophilum), MEROPS Accession MER0000547 (peptidase unit: 35-200); PDB accession 1PMA_A |
| History | MEROPS 1.202 (17 June 1997) |
| Description | Threonine, serine or cysteine nucleophile at the N-terminus of mature enzyme |
| Contents of clan | Clan PB contains endopeptidases and self-processing proteins. |
| Evidence | Families are assigned to clan PB on the basis of similar protein folds (see below) or an N-terminally-placed catalytic nucleophile (see the Alignment). |
| Catalytic mechanism | The clan contains cysteine, serine and threonine peptidases. The N-terminal residue of the mature protein is catalytic, being the nucleophile and general base (the amino group). For this reason, proteins with this fold are known as N-terminal nucleophile (Ntn) hydrolases. |
| Peptidase activity | In all families except T1, the peptidase activity is restricted to an autolytic activation of the precursor protein, and once the mature protein is generated it ceases to have peptidase activity. |
| Protein fold | Peptidases in clan PB have a fold consisting of four layers: alpha/beta/beta/alpha. |
| Homologous non-peptidase families | The fold is unique to clan PB. Some families in clan PB contain proteins that have no peptidase activity because the only proteolytic activation required is removal of an initiating Met, which is performed by methionyl aminopeptidase (M24.001). |
| Activation mechanism | The peptidases in clan PB are all activated autolytically, exposing an N-terminal nucleophile. |
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Other databases
| PFAM | CL0052 |
|
| SCOP | 56235 |
Families
| C44 |
amidophosphoribosyltransferase precursor (Homo sapiens) |
Yes |
| C45 |
acyl-coenzyme A:6-aminopenicillanic acid acyl-transferase precursor (Penicillium chrysogenum) |
Yes |
| C59 |
penicillin V acylase precursor (Lysinibacillus sphaericus) |
Yes |
| C69 |
dipeptidase A (Lactobacillus helveticus) |
- |
| C89 |
acid ceramidase precursor (Homo sapiens) |
- |
| C95 |
lysosomal 66.3 kDa protein ({Mus musculus}-type) (Mus musculus) |
- |
| S45 |
penicillin G acylase precursor (Escherichia coli) |
Yes |
| T01 |
archaean proteasome, beta component (Thermoplasma acidophilum) |
Yes |
| T02 |
glycosylasparaginase precursor (Homo sapiens) |
Yes |
| T03 |
gamma-glutamyltransferase 1 (bacterial-type) (Escherichia coli) |
Yes |
| T07 |
CwpV ({Clostridium difficile}) self-cleaving threonine peptidase (Peptoclostridium difficile) |
- |
Distribution of clan PB among Kingdoms of Organisms
