Summary for clan SF

Summary Structure Literature
Clan type peptidaseS24.003 - UmuD protein (Escherichia coli), MEROPS Accession MER0000576 (peptidase unit: 25-139); PDB accession 1UMU
HistoryMethods Enzymol. 244:461-486 (1994)
DescriptionSerine nucleophile; catalytic residues in the order Ser, Lys (or His) in sequence
Contents of clanClan SF contains endopeptidases, some of which are self-processing proteins.
EvidenceFamilies S24 and S26 are united in the clan by their similar protein folds (see below) and the similar catalytic residues.
Catalytic mechanismCatalytic residues occur in the order Ser, Lys or His (see the Alignment). The catalytic mechanism has been discussed by Paetzel et al. (2002).
Peptidase activityIn many cases, specificity favours an alanine P1 residue. (See also families S24 and S26.)
Protein foldTertiary structures have been determined for members of families S24 (repressor LexA, S24.001; Luo et al., 2001) and S26 (signal peptidase 1, S26.001; Paetzel et al., 1995). Peptidases in the clan are predominantly all-beta proteins, containing several coiled beta sheets and a beta barrel. Members of family S24 have an additional C-terminal domain containing a bundle of three helices presumably important for binding DNA.
Homologous non-peptidase familiesThe fold is unique to the clan.
Activation mechanismThe autolytic cleavage of LexA (S24.001) is promoted by formation of a complex that involves the protein RecA, or by alkaline conditions (Little, 1993).
Other databases SCOP51306


Family Family Type Peptidase Structure
S24 repressor LexA (Escherichia coli) Yes
S26 signal peptidase I (Escherichia coli) Yes

Distribution of clan SF among Kingdoms of Organisms