Summary for clan PB

Summary Alignment Structure Literature
Clan type peptidaseT01.970 - archaean proteasome, alpha component (Thermoplasma acidophilum), MEROPS Accession MER0000547 (peptidase unit: 35-200); PDB accession 1PMA_A
HistoryMEROPS 1.202 (17 June 1997)
DescriptionThreonine, serine or cysteine nucleophile at the N-terminus of mature enzyme
Contents of clanClan PB contains endopeptidases and self-processing proteins.
EvidenceFamilies 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 mechanismThe 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 activityIn 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 foldPeptidases in clan PB have a fold consisting of four layers: alpha/beta/beta/alpha.
Homologous non-peptidase familiesThe 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 mechanismThe peptidases in clan PB are all activated autolytically, exposing an N-terminal nucleophile.
Other databases PFAMCL0052
SCOP56235

Families

Family Family Type Peptidase Structure
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

FamilyBacteriaArchaeaProtozoaFungiPlantsAnimalsViruses
C44+++++++
C45++++++-
C59++-++++
C69++++++-
C89+-+++++
C95+++-++-
P2--+--+-
S45+++-++-
T1+++++++
T2++++++-
T3+++++++
T7+---++-
Clan+++++++