Summary for clan SB

Summary Alignment Structure Literature
Clan type peptidaseS08.001 - subtilisin Carlsberg (Bacillus licheniformis), MEROPS Accession MER0000309 (peptidase unit: 106-379); PDB accession 1SCN
HistoryMethods Enzymol. 244:461-486 (1994)
DescriptionSerine nucleophile; catalytic residues in the order Asp, His, Ser in sequence in family S8, but family S53 differs
Contents of clanClan SB contains endopeptidases and exopeptidases.
Evidence(See protein fold.)
Catalytic mechanismThe catalytic mechanisms of the families of clan SB are different. In family S8 the active site residues form a catalytic triad in the order Asp, His, Ser whereas family S53 contains a catalytic tetrad in the order Glu, Asp, Asp, Ser. Only the Ser in both families and the His in family S8 and the Glu in family S53 are in equivalent positions. The Ser in both families is found within a Gly-Thr-Ser-Xaa-Xaa-Xbb-Pro motif (where Xaa is an aliphatic amino acid and Xbb is a small amino acid (Ser/Thr/Ala/Gly)). See Rawlings and Barrett, (2004) for more information.
Peptidase activityThe clan contains endopeptidases, exopeptidases and also a tripeptidyl-peptidase (S53.003).
Protein foldThe structure of subtilisin BPN" (S08.034) was one of the first tertiary structures to be resolved (Wright et al., 1969). Peptidases in clan SB are alpha/beta proteins with a seven stranded beta sheet sandwiched between two layers of helices. All the strands in the sheet are parallel and occur in the order 2314567. The active site Ser occurs in the motif Gly-Thr-Ser-Xaa-Ala-Xbb-Pro where Xaa is an aliphatic hydrophobic and Xbb is a small amino acid. The first structure determined from family S53 was that of kumamolysin (S53.004), which show a subtilisin-like fold.
Homologous non-peptidase familiesThe fold is unique to peptidases of clan SB.
Other databases SCOP52743


Family Family Type Peptidase Structure
S8 subtilisin Carlsberg (Bacillus licheniformis) Yes
S53 sedolisin (Pseudomonas sp. 101) Yes

Distribution of clan SB among Kingdoms of Organisms