Family C75

Family

Summary Holotypes Alignment Tree Genomes Literature Architecture

Summary for family C75

Family type peptidase	C75.001 - AgrB peptidase (Staphylococcus aureus), MEROPS Accession MER0043287 (peptidase unit: 1-189)
Content of family	Peptidase family C75 contains endopeptidases.
History	Identifier created: MEROPS 8.0 (8 January 2008) The operon of the accessory gene regulator (agr) of Staphylococcus aureus encodes four genes (agrA, B, C, and D) whose products compose a quorum sensing system. AgrA and AgrC resemble a two-component signal-transduction system of which AgrC is a sensor kinase and AgrA is a response regulator. AgrD is a polypeptide that is integrated into the cytoplasmic membrane via its N-terminal region, and is the precursor for an autoinducing peptide (AIP) that is the ligand for AgrC. Zhang et al. (2002) speculated that AgrB is a proteolytic enzyme responsible for the processing of AgrD to liberate the AIP, and this has been confirmed by later work (Qiu et al. (2005); Kavanaugh et al., 2007).
Catalytic type	Cysteine
Active site residues	H77 C84
Active site	The catalytic residues identified in Staphylococcus aureus AgrB by Qiu et al. (2005) are His77 and Cys84.
Activities and specificities	The AIP is derived from the central region of the AgrD sequence, so the processing involves removal of both N-terminal and C-terminal extensions. AgrB cleaves off the C-terminus, and the N-terminus is cleaved by the signal peptidase, SpsB (S26.016) (Kavanaugh et al., 2007).
Inhibitors	Inhibition was observed with several peptidyl chloromethanes, but not E64 (Qiu et al., 2005).
Molecular structure	AgrB is an integral membrane protein. No three-dimensional structure is available, but the way in which it may be inserted into the bacterial membrane has been described by Zhang & Ji (2004). This model places the active site residues in or close to the cytoplasm.
Clan	unassigned

Distribution of family	Bacteria	details
	Archaea	-
	Protozoa	-
	Fungi	-
	Plants	-
	Animals	-
	Viruses	-

Biological functions	The peptidases in family C75 contribute to the synthesis of bacterial autoinducing peptides by cleavage of precursor proteins (Qiu et al., 2005; Kavanaugh et al., 2007).
Statistics for family C75	Sequences:	121
	Identifiers:	2
	Identifiers with PDB entries:	0
Downloadable files	Sequence library (FastA format)
	Sequence alignment (FastA format)
	Phylogenetic tree (Newick format)

Other databases	INTERPRO	IPR006741
	PFAM	PF04647

Peptidases and Homologues	MEROPS ID	Structure
AgrB peptidase	C75.001	-
FsrB peptidase (Enterococcus faecalis)	C75.002	-
Family C75 non-peptidase homologues	non-peptidase homologue	-
Family C75 unassigned peptidases	unassigned	-