The accessory gene regulator (agr) of Staphylococcus aureus is the central regulatory system that controls the gene expression for a large set of virulence factors. The arg locus consists of two transcripts: RNAII and RNAIII. RNAII encodes four genes (agrA, B, C, and D) whose gene products assemble a quorum sensing system. At low cell density, the agr genes are continuously expressed at basal levels. A signal molecule, autoinducing peptide (AIP), produced and secreted by the bacteria, accumulates outside of the cells. When the cell density increases and the AIP concentration reaches a threshold, it activates the agr response, i.e. activation of secreted protein gene expression and subsequent repression of cell wall-associated protein genes. AgrB and AgrD are essential for the production of the autoinducing peptide which functions as a signal for quorum sensing. AgrB is a transmembrane protein (PUBMED:11195102). AgrB is involved in the proteolytic processing of AgrD and may have both proteolytic enzyme activity and a transporter facilitating the export of the processed AgrD peptide (PUBMED:12122003).
The accessory gene regulator (agr) of Staphylococcus aureus is the central regulatory system that controls the gene expression for a large set of virulence factors. The arg locus consists of two transcripts: RNAII and RNAIII. RNAII encodes four genes (agrA, B, C, and D) whose gene products assemble a quorum sensing system. At low cell density, the agr genes are continuously expressed at basal levels. A signal molecule, autoinducing peptide (AIP), produced and secreted by the bacteria, accumulates outside of the cells. When the cell density increases and the AIP concentration reaches a threshold, it activates the agr response, i.e. activation of secreted protein gene expression and subsequent repression of cell wall-associated protein genes. AgrB and AgrD are essential for the production of the autoinducing peptide which functions as a signal for quorum sensing. AgrB is a transmembrane protein [(PUBMED:11195102)] involved in the proteolytic processing of AgrD, and may have both proteolytic and transporter activities, facilitating the export of the processed AgrD peptide [(PUBMED:12122003)].
High genetic variability of the agr locus in Staphylococcus species.
J Bacteriol. 2002; 184: 1180-6
Display abstract
The agr quorum-sensing and signal transduction system was initially described in Staphylococcus aureus, where four distinct allelic variants have been sequenced. Western blotting suggests the presence of homologous loci in many other staphylococci, and this has been confirmed for S. epidermidis and S. lugdunensis. In this study we isolated agr-like loci from a range of staphylococci by using PCR amplification from primers common to the six published agr sequences and bracketing the most variable region, associated with quorum-sensing specificity. Positive amplifications were obtained from 14 of 34 staphylococcal species or subspecies tested. Sequences of the amplicons identified 24 distinct variants which exhibited extensive sequence divergence with only 10% of the nucleotides absolutely conserved on multiple alignment. This variability involved all three open reading frames involved in quorum sensing and signal transduction. However, these variants retained several protein signatures, including the conserved cysteine residue of the autoinducing peptide, with the exception of S. intermedius of pigeon origin, which contained a serine in place of cysteine at this position. We discuss hypotheses on the mode of action and the molecular evolution of the agr locus based on comparisons between the newly determined sequences.
Transmembrane topology of AgrB, the protein involved in the post-translational modification of AgrD in Staphylococcus aureus.
J Biol Chem. 2002; 277: 34736-42
Display abstract
The accessory gene regulator (agr) of Staphylococcus aureus is the central regulatory system that controls the gene expression for a large set of virulence factors. This global regulatory locus consists of two transcripts: RNAII and RNAIII. RNAII encodes four genes (agrA, B, C, and D) whose gene products assemble a quorum sensing system. RNAIII is the effector of the Agr response. Both the agrB and agrD genes are essential for the production of the autoinducing peptide, which functions as a signal for the quorum sensing system. In this study, we demonstrated the transmembrane nature of AgrB protein in S. aureus. A transmembrane topology model of AgrB was proposed based on AgrB-PhoA fusion analyses in Escherichia coli. Two hydrophilic regions with several highly conserved positively charged amino acid residues among various AgrBs were found to be located in the cytoplasmic membrane as suggested by PhoA-AgrB fusion studies. However, this finding is inconsistent with the putative transmembrane profile of AgrB by computer analysis. Furthermore, we detected an intermediate peptide of processed AgrD from S. aureus cells expressing AgrB and a 6 histidine-tagged AgrD. These results provide direct evidence that AgrB is involved in the proteolytic processing of AgrD. We speculate that AgrB is a novel protein with proteolytic enzyme activity and a transporter facilitating the export of the processed AgrD peptide.
Inducible expression and cellular location of AgrB, a protein involved in the maturation of the staphylococcal quorum-sensing pheromone.
Arch Microbiol. 2000; 174: 452-5
Display abstract
AgrB has been suggested to be responsible for the posttranslational modification in staphylococci that leads to the production of the thiolactone-containing agr peptide pheromone. We demonstrate that AgrB is located in the cytoplasmic membrane. Vectors were constructed for the xylose-inducible overexpression of agrB, and of agrB and agrD together. A Staphylococcus epidermidis strain deleted for agr and containing these vectors was assayed for AgrB protein and pheromone production. The lack of adequate pheromone production suggests the involvement of additional factors in the production of the agr pheromone.
Metabolism (metabolic pathways involving proteins which contain this domain)
This information is based on mapping of SMART genomic protein database to KEGG orthologous groups. Percentage points are related to the number of proteins with AgrB domain which could be assigned to a KEGG orthologous group, and not all proteins containing AgrB domain. Please note that proteins can be included in multiple pathways, ie. the numbers above will not always add up to 100%.
Links (links to other resources describing this domain)
to expand nodes. To display all proteins with a AgrB domain in a specific node, click on it.