agr signal receptor in Staphylococcus aureus
Transmembrane topology and histidine protein kinase activity of AgrC, the
The agr P2 operon in Staphylococcus aureus codes for the elements of a density-sensing cassette made up of a typical two-component signalling system and its corresponding inducer. It is postulated that the autoinducer, a post-translationally modified octapeptide generated from the AgrD peptide, interacts with a receptor protein, coded by agrC, to transmit a signal via AgrA regulating expression of staphylococcal virulence genes through expression of agr RNA III. We show by analysis of PhoA fusions that AgrC is a transmembrane protein, and confirm using Western blotting that a 46 kDa protein corresponding to AgrC is present in the bacterial membrane. This protein is autophosphorylated on a histidine residue only in response to supernatants from an agr+ strain, and can also respond to the purified native octapeptide. A recombinant fusion protein where most of the N-terminal region of AgrC is replaced by the Escherichia coli maltose-binding protein is also autophosphorylated in response to stimulation by agr+ supernatants or purified octapeptide. We conclude that AgrC is the sensor molecule of a typical two-component signal system in S. aureus, and that the ligand-binding site of AgrC is probably located in the third extracellular loop of the protein.
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Document Type: Original Article
UPRES EA1655, Faculté de Médecine Laennec, Rue Guillaume Paradin, 69372 Lyon Cedex 08, France.,
Skirball Institute of Biomolecular Medicine, New York University Medical Center, New York, NY 10016, USA.,
Laboratoire d'Immunologie et Biologie Pulmonaire, Hôpital Cardiologique Louis Pradel, BP Lyon Montchat, 69394 Lyon Cedex 03, France.
April 1, 1998