Inducible expression and cellular location of AgrB, a protein involved in the maturation of the staphylococcal quorum-se
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S H O RT C O M M U N I C AT I O N
Henri L. Saenz · Vera Augsburger · Cuong Vuong · Ralph W. Jack · Friedrich Götz · Michael Otto
Inducible expression and cellular location of AgrB, a protein involved in the maturation of the staphylococcal quorum-sensing pheromone Received: 5 April 2000 / Revised: 22 September 2000 / Accepted: 22 September 2000 / Published online: 18 November 2000 © Springer-Verlag 2000
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. Keywords agr · Quorum-sensing · Staphylococcus epidermidis · Pheromone · Posttranslational modification
Introduction Bacterial quorum-sensing systems regulate protein expression in response to population density in order to cope with changing environmental conditions (Swift et al. 1996). In Staphylococcus aureus and in Staphylococcus epidermidis, the agr quorum-sensing system is responsible for the drastic alteration of exoprotein and surface protein expression during the switch from the exponential growth phase to the stationary phase (Kornblum et al. 1990; Vuong et al. 2000). These changes are believed to also be important for the survival of the two pathogenic bacterial strains during infection (Novick and Muir 1999). The quorum-sensing mechanism involves the production and sensing of an auto-inducing signal or pheromone. We have recently shown that the S. epidermidis quorumsensing pheromone, which is the maturation product of
H. L. Saenz · V. Augsburger · C. Vuong · R. W. Jack · F. Götz · M. Otto (✉) Mikrobielle Genetik, Universität Tübingen, Waldhäuserstr. 70/8, 72076 Tübingen, Germany e-mail: [email protected], Tel.: +49-7071-2975938, Fax: +49-7071-295937
the AgrD precursor peptide, is a cyclic peptide harboring a thiolactone structure by demonstration of the biological activity of chemically synthesized pheromone (Otto et al. 1998). The thiolactone structure has meanwhile also been proven for S. aureus using the same approach (Mayville et al. 1999). The agr system has been found in many staphylococcal species (Kornblum et al. 1990; Otto et al. 1998; Vandenesch et al. 1993) and is composed of two transcriptional units, one coding for a regulatory RNA molecule, RNAIII, the other coding for the genes agrA, agrB, agrC, and agrD. Sequence analysis of AgrB suggests that it is membrane-located. No significant sequence similarities to known proteins have been found in the databases. Introduction of the agrB gene together with the agrD gene of S. aureus in agr-deficient strains resulted in
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