Summary for clan SF

Clan type peptidase	S24.003 - UmuD protein (Escherichia coli), MEROPS Accession MER0000576 (peptidase unit: 25-139); PDB accession 1UMU
History	Methods Enzymol. 244:461-486 (1994)
Description	Serine nucleophile; catalytic residues in the order Ser, Lys (or His) in sequence
Contents of clan	Clan SF contains endopeptidases, some of which are self-processing proteins.
Evidence	Families S24 and S26 are united in the clan by their similar protein folds (see below) and the similar catalytic residues.
Catalytic mechanism	Catalytic residues occur in the order Ser, Lys or His (see the Alignment). The catalytic mechanism has been discussed by Paetzel et al. (2002).
Peptidase activity	In many cases, specificity favours an alanine P1 residue. (See also families S24 and S26.)
Protein fold	Tertiary 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 families	The fold is unique to the clan.
Activation mechanism	The 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	SCOP	51306

Families

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