Key points are not available for this paper at this time.
The accessory gene regulator (agr) ofStaphylococcus 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 theagrB 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. The accessory gene regulator (agr) ofStaphylococcus 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 theagrB 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. Staphylococcus aureus is an important bacterial pathogen that causes a great variety of human diseases. The pathogenicity of S. aureus largely depends on a set of virulence factors. These include cell wall-associated proteins involved in attaching the bacteria to host cells or extracellular matrices and protecting the bacteria against host defenses. Other factors are secreted proteins that attack host cells, degrade components of extracellular matrices, and interfere with immune responses (1Projan S.J. Novick R.P. Crossley K.B. Archer G.L. The Staphylococci in Human Disease. Churchill Livingstone, New York1997: 55-81Google Scholar). The expression of these virulence factor genes is primarily regulated by a quorum sensing system encoded by the global regulatory locus, the accessory gene regulator (agr). At low cell density, theagr genes are continuously expressed at basal levels. A signal molecule, autoinducing peptide (AIP), 1The abbreviations used are: AIP, autoinducing peptide; agr , accessory gene regulator; BlaZ, β-lactamase; PblaZ, blaZ promoter; PhoA, alkaline phosphatase; Tricine, N-2-hydroxy-1,1-bis(hydroxymethyl)ethylglycine; DAS, Dense Alignment Surface. produced and secreted by the bacteria, accumulates outside of the cells (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 3Ji G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar). When the cell density increases and the AIP concentration reaches a threshold, it activates the agr response (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar), i.e. activation of secreted protein gene expression and subsequent repression of cell wall-associated protein genes (1Projan S.J. Novick R.P. Crossley K.B. Archer G.L. The Staphylococci in Human Disease. Churchill Livingstone, New York1997: 55-81Google Scholar, 4Novick R.P. Dunny G.M. Winans S.C. Cell-Cell Signaling in Bacteria. American Society for Microbiology, Washington, D. C.1999: 129-146Google Scholar, 5Novick R.P. Fischetti V.A. Novick R.P. Ferretti J.J. Portnoy D.A. Rood J.I. Gram-Positive Pathogens. American Society for Microbiology, Washington, D. C.2000: 392-407Google Scholar, 6Janzon L. Arvidson S. EMBO J. 1990; 9: 1391-1399Crossref PubMed Scopus (228) Google Scholar). The agr locus consists of two operons, P2 and P3 (6Janzon L. Arvidson S. EMBO J. 1990; 9: 1391-1399Crossref PubMed Scopus (228) Google Scholar, 7Novick R.P. Projan S.J. Kornblum J. Ross H.F., Ji, G. Kreiswirth B. Vandenesch F. Moghazeh S. Mol. Gen. Genet. 1995; 248: 446-458Crossref PubMed Scopus (330) Google Scholar). The P3 transcript, RNA III, the effector of the agr response, functions as the regulator controlling the expression of virulence factor genes by a yet to be defined mechanism (6Janzon L. Arvidson S. EMBO J. 1990; 9: 1391-1399Crossref PubMed Scopus (228) Google Scholar, 8Novick R.P. Ross H.F. Projan S.J. Kornblum J. Kreiswirth B. Moghazeh S. EMBO J. 1993; 12: 3967-3975Crossref PubMed Scopus (831) Google Scholar, 9Zhang S. Stewart G.C. J. Bacteriol. 2000; 182: 2321-2325Crossref PubMed Scopus (28) Google Scholar, 10Chan P.F. Foster S.J. Microbiology. 1998; 144: 2469-2479Crossref PubMed Scopus (110) Google Scholar, 11Benito Y. Kolb F.A. Romby P. Lina G. Etienne J. Vandenesch F. RNA (N. Y.). 2000; 6: 668-679Crossref PubMed Scopus (133) Google Scholar, 12Tegmark K. Morfeldt E. Arvidson S. J. Bacteriol. 1998; 180: 3181-3186Crossref PubMed Google Scholar). The P2 transcript, RNA II, encodes four genes, agrA, B,C, and D (6, 7). AgrC, a transmembrane protein, is a sensor kinase of the classic bacterial two component signal transduction system: the N-terminal half is the input domain that interacts with a signal molecule produced by the bacteria, and the C-terminal half is a transmitter that is autophosphorylated at a conserved histidine upon stimulation by the signal molecule (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 13Lina G. Jarraud S., Ji, G. Greenland T. Pedraza A. Etienne J. Novick R.P. Vandenesch F. Mol. Microbiol. 1998; 28: 655-662Crossref PubMed Scopus (197) Google Scholar,14Lyon G.J. Wright J. Christopoulos A. Novick R.P. Muir T.W. J. Biol. Chem. 2002; 277: 6247-6253Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar). AgrA resembles a response regulator, which is required for the activation of both agr promoters P2 and P3 (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 7Novick R.P. Projan S.J. Kornblum J. Ross H.F., Ji, G. Kreiswirth B. Vandenesch F. Moghazeh S. Mol. Gen. Genet. 1995; 248: 446-458Crossref PubMed Scopus (330) Google Scholar, 15Peng H.L. Novick R.P. Kreiswirth B. Kornblum J. Schlievert P. J. Bacteriol. 1988; 170: 4365-6372Crossref PubMed Scopus (416) Google Scholar), although it is not clear whether AgrA binds to these two promoters directly (16Morfeldt E. Panova-Sapundjieva I. Gustafsson B. Arvidson S. FEMS Microbiol. Lett. 1996; 143: 195-201Crossref PubMed Google Scholar, 17Morfeldt E. Tegmark K. Arvidson S. Mol. Microbiol. 1996; 21: 1227-1237Crossref PubMed Scopus (143) Google Scholar). It is possible that either phosphorylated AgrA would bind to the agr promoters or AgrA would interact with another global regulator, SarA, to control the agrexpression (17Morfeldt E. Tegmark K. Arvidson S. Mol. Microbiol. 1996; 21: 1227-1237Crossref PubMed Scopus (143) Google Scholar, 18Cheung A.L. Projan S.J. J. Bacteriol. 1994; 176: 4168-4172Crossref PubMed Google Scholar, 19Cheung A.L. Bayer M.G. Heinrichs J.H. J. Bacteriol. 1997; 179: 3963-3971Crossref PubMed Google Scholar). Both agrB and agrD genes are essential for the production of the signal molecule, AIP (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 3Ji G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar). The AgrD propeptide is ribosomally synthesized and subsequently processed and secreted from the bacteria (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 3Ji G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar, 20Novick R.P. Muir T.W. Curr. Opin. Microbiol. 1999; 2: 40-45Crossref PubMed Scopus (131) Google Scholar). The AIP is a thiolactone molecule containing a ring of 5 amino acids formed by a thioester linkage between the sulfhydryl group of a cysteine and the C-terminal and a from to amino acid residues on and the G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar, R. G. F. Lett. 1998; PubMed Scopus Google Scholar, Ji, G. Beavis R. Novick R.P. Muir T.W. Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar, S. G.J. L. Vandenesch F. Etienne J. Muir T.W. Novick R.P. J. Bacteriol. 2000; 182: PubMed Scopus Google Scholar). This thioester is for agr activation activity G.J. Wright J. Christopoulos A. Novick R.P. Muir T.W. J. Biol. Chem. 2002; 277: 6247-6253Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar, R. G. F. Lett. 1998; PubMed Scopus Google Scholar, Ji, G. Beavis R. Novick R.P. Muir T.W. Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar, P. S.J. S. A. P. Mol. Microbiol. PubMed Scopus Google Scholar). AgrB is to be a transmembrane protein R.P. Projan S.J. Kornblum J. Ross H.F., Ji, G. Kreiswirth B. Vandenesch F. Moghazeh S. Mol. Gen. Genet. 1995; 248: 446-458Crossref PubMed Scopus (330) Google Scholar), and the of Staphylococcus AgrB with the cell membrane demonstrated H.L. F. Microbiol. 2000; PubMed Scopus Google Scholar). AgrB is required for the production of AIP (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 3Ji G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar). the production of AIP several proteolytic thioester and we that AgrB was the protein to these In this study, we the membrane and proposed the transmembrane topology aureus we direct evidence that AgrB was involved in the proteolytic processing of AgrD. S. aureus and used in this are in S. aureus cells were in R.P. PubMed Scopus Google Scholar), with 5 5 at on R.P. PubMed Scopus Google were used to of cells was with either a with a or a at of genes by was with Escherichia J. A was in and with aureus and used in this and a R.P. Ross H.F. Projan S.J. Kornblum J. Kreiswirth B. Moghazeh S. EMBO J. 1993; 12: 3967-3975Crossref PubMed Scopus (831) Google R.P. Ross H.F. Projan S.J. Kornblum J. Kreiswirth B. Moghazeh S. EMBO J. 1993; 12: 3967-3975Crossref PubMed Scopus (831) Google R.P. Projan S.J. Kornblum J. Ross H.F., Ji, G. Kreiswirth B. Vandenesch F. Moghazeh S. Mol. Gen. Genet. 1995; 248: 446-458Crossref PubMed Scopus (330) Google in G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google agrB in G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google agrD in G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google agrB in in in agrB in in in R.P. Ross H.F. Projan S.J. Kornblum J. Kreiswirth B. Moghazeh S. EMBO J. 1993; 12: 3967-3975Crossref PubMed Scopus (831) Google R.P. Ross H.F. Projan S.J. Kornblum J. Kreiswirth B. Moghazeh S. EMBO J. 1993; 12: 3967-3975Crossref PubMed Scopus (831) Google in a S. used in this were based on either or R.P. Projan S.J. Kornblum J. Ross H.F., Ji, G. Kreiswirth B. Vandenesch F. Moghazeh S. Mol. Gen. Genet. 1995; 248: 446-458Crossref PubMed Scopus (330) Google was by (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google and with large and A from containing agrB gene the control of the was of to to the C-terminal AgrB expression a with and histidine and a as and as the was The was with and the with of was by a containing gene the control of the from (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google was as a with an and as and (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google as the was with and and with of A containing and the of agrD was with the of and as and as the This was with and the and with of in the the with and as and as the was with and and with of The the for a bacterial and 6 histidine residues at the of AgrD. Both the N-terminal and the C-terminal AgrD was by with the the AgrD and the 6 histidine and and as the This was with and with to The of products used were by of were by either the R.P. PubMed Scopus Google or S. FEMS Microbiol. Lett. PubMed Google Scholar). AIP activity was to the (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google that S. aureus cells expressing AgrD and AgrB or AgrD and AgrB the control of the were with at for 5 products the in and the an and as the were with and and the of the E. fusion or by of The were E. The between agrB and and theagrB of was by activity was cell in The was as Wright A. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). S. aureus cells were in and with at for the cell was in R.P. PubMed Scopus Google containing and for at The were and by of with and and on for The cell was and the cells were by at for at The cell was at at to the cell membrane and cytoplasmic The membrane was with in and at concentration was with a protein E. cells containing expression or were in at with cell were by in of and The of the cell was by at for at The were in J. A Scholar), for 5 and at proteins were with the of to the was directly to the protein to the cell cytoplasmic or protein were for 5 in were either by J. 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The of the 6 histidine residues on the AgrB processing of AgrD was as were from cells expressing AgrD or both AgrB and AgrD In were from cells expressing the AgrB and AgrD The AIP in the were produced AIP activity with that of not that the C-terminal AgrB in S. aureus. the of the AgrB protein in S. cytoplasmic and membrane were by from or with as a that the as detected in the cell of in the membrane of the not this with was to proteins from the cytoplasmic and membrane of or This the protein in the membrane from cells expressing the AgrB not These with a on the S. AgrB H.L. F. Microbiol. 2000; PubMed Scopus Google Scholar), that AgrB is located in the cytoplasmic in AgrB-PhoA of AgrB proteins from the four of S. G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar, S. G.J. L. Vandenesch F. Etienne J. Muir T.W. Novick R.P. J. Bacteriol. 2000; 182: PubMed Scopus Google as as the AgrB from S. R. G. F. Lett. 1998; PubMed Scopus Google and Staphylococcus F. Projan S.J. Kreiswirth B. Etienne J. Novick R.P. FEMS Microbiol. Lett. 1993; PubMed Google were A J. J. Mol. Biol. PubMed Scopus Google for these AgrB proteins is in A. The AgrB proteins were with various the These include G. J. Mol. Biol. PubMed Scopus Google A. B. G. J. Mol. Biol. PubMed Scopus Google and Dense Alignment E. I. G. A. 1997; PubMed Google the highly among the results in although the transmembrane were for A of possible transmembrane were from these the topology from the various of the or the of theagrB gene from were by and the E. fusion or a of A of fusion were The expression of the fusion proteins in E. the fusion was by of cell with a to the of the fusion proteins were of to the of the with proteins not the from cell were used for analysis. This of the membrane proteins not of the proteins are highly expressed as in these in which the fusion proteins are expressed the control of a on a A was used by H.L. F. Microbiol. 2000; PubMed Scopus Google to S. in the AgrB-PhoA fusion proteins with the were The of the fusion proteins expressed in were although in a were of A protein with an of was in the that it be a or The alkaline activity of expressing the AgrB-PhoA fusion protein was The of the fusion of fusion protein was based on the that the the fusion of the protein, is in the that the fusion is either in the membrane or in the The and to that the N-terminal of a highly hydrophilic was in the We that AgrB not to a signal peptide at N-terminal of AgrB from amino acid residues to on the of AgrB S. and G. Ji, The AgrB-PhoA fusion that the of AgrB is in the The transmembrane II, and from the computer were based on the activity of and and and and and However, both and to be in the transmembrane that both and were this was located outside of the cytoplasmic and and and these amino acid residues were either in the transmembrane or in the both the and the were in the it was to the regions from to and from to as transmembrane on these AgrB-PhoA fusion results and computer a putative AgrB transmembrane topology model was as in B. In this the AgrB protein transmembrane Two of highly hydrophilic amino acid residues and a highly outside of the We that the agrB gene is required for the production of the AIP in (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 3Ji G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar), direct evidence the of AgrB in the proteolytic processing of AgrD the of AgrB in this we a in which 6 histidine were to the of agrD gene and a containing as as a was at the A of the AgrD fusion protein is in A. S. aureus expressing both AgrB and produced AIP, although the AIP activity was that of expressing the AgrB and AgrD the fusion protein was with was cell from cells expressing with or in a of in to the of was from cells expressing and not from cells not expressing protein with an of from cells expressing both AgrB and This protein was detected in the with cell and as a These results that the protein was an of the and the N-terminal of AgrD and that AgrB was required for the production of this However, it was not clear whether the protein was an intermediate or a or whether AgrB or AgrB with this proteolytic in of and another of in was in both This protein was the that this protein was a of the protein and the was the N-terminal of AgrD. the agr system the expression of a of virulence of theagr gene expression among or of the of by AIP great in controlling the pathogenicity G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar, 4Novick R.P. Dunny G.M. Winans S.C. Cell-Cell Signaling in Bacteria. American Society for Microbiology, Washington, D. C.1999: 129-146Google Scholar, 5Novick R.P. Fischetti V.A. Novick R.P. Ferretti J.J. Portnoy D.A. Rood J.I. Gram-Positive Pathogens. American Society for Microbiology, Washington, D. C.2000: 392-407Google Scholar, 20Novick R.P. Muir T.W. Curr. Opin. Microbiol. 1999; 2: 40-45Crossref PubMed Scopus (131) Google Scholar). on the and activity of the G.J. Wright J. Christopoulos A. Novick R.P. Muir T.W. J. Biol. Chem. 2002; 277: 6247-6253Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar, Ji, G. Beavis R. Novick R.P. Muir T.W. Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar, P. S.J. S. A. P. Mol. Microbiol. PubMed Scopus Google Scholar, G.J. P. Muir T.W. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 2000; PubMed Scopus Google Scholar), it AgrD is to the that agrB encodes a protein required for the processing of the AgrD and the of AgrB and both the required for of the peptide of AgrD (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 3Ji G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar, 4Novick R.P. Dunny G.M. Winans S.C. Cell-Cell Signaling in Bacteria. American Society for Microbiology, Washington, D. C.1999: 129-146Google Scholar). In this study, we expressed AgrB in S. aureus and that AgrB is in the cytoplasmic These results are with a on the AgrB from S. H.L. F. Microbiol. 2000; PubMed Scopus Google Scholar). AgrD is processed in a it proteolytic of the propeptide at two by the of a thioester and the (2Ji G. Beavis R. Novick R.P. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12055-12059Crossref PubMed Scopus (519) Google Scholar, 3Ji G. Beavis R. Novick R.P. Science. 1997; 276: 2027-2030Crossref PubMed Scopus (630) Google Scholar, Ji, G. Beavis R. Novick R.P. Muir T.W. Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar). In the that AgrB is required for the production of the AIP molecule, which accumulates outside of the cells, it to that AgrB be involved in these the of the of AgrB is to the mechanism of the AgrD processing by the AgrB protein and to the of that important in the AgrD The AgrB membrane topology we proposed in this was based on the fusion analyses in E. in with analysis. a fusion used in transmembrane topology as the membrane topology of a protein involved in both and of J. G. J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar), and aureus membrane proteins G. Jarraud S., Ji, G. Greenland T. Pedraza A. Etienne J. Novick R.P. Vandenesch F. Mol. Microbiol. 1998; 28: 655-662Crossref PubMed Scopus (197) Google Scholar, J. Bacteriol. 1997; 179: PubMed Google Scholar, Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google Scholar). fusion results that four of the were transmembrane as by computer analysis. The between and was as an outside based on the of and However, an intermediate of alkaline that this of the AgrB protein was not was in intermediate i.e. a be in a between the and the this of AgrB an important in the of AIP or in the processing of the AgrD propeptide and of and alkaline although these fusion were located in two highly hydrophilic were possible to these two are It that a fusion to a domain low alkaline activity of the of a positively charged in the to the N-terminal J. J. Mol. Biol. PubMed Scopus Google Scholar). However, this would not both are by fusion that are are in the the of the four transmembrane by fusion analyses this are transmembrane The is not a for the of a transmembrane by K. G. K. Mol. 1998; 2: Full Text Full Text PDF PubMed Scopus Google Scholar), an with topology is to a hydrophilic the membrane membrane proteins are the We that the of these two regions in the membrane is and would be with the of the AgrB membrane topology is both regions highly conserved positively charged amino acid residues among the AgrBs we that the two hydrophilic transmembrane are in the four transmembrane and this be for the processing and of AgrD peptide. We direct evidence that AgrB is involved in the proteolytic processing of AgrD. We not the that be with AgrB with the activity to this The from AgrD propeptide in the of AgrB to be to the AgrD. The or of AgrB involved in the proteolytic processing of AgrD not However, results although the AIP is the possible products by AgrB and the AgrD propeptide were and these were not found either in the or in the were detected in the of AgrB and These results that the AgrD proteolytic processing the It is possible that this either in the or outside of the cytoplasmic and the processing products with the of the AIP It would be to the fusion we to the possible AgrB in E. coli. However, to AIP from E. cells expressing AgrB and AgrD were not The for this is not We that in bacteria that peptide to the quorum sensing as in Mol. Microbiol. 1997; PubMed Scopus Google Scholar), D.A. Mol. Microbiol. 1996; 21: PubMed Scopus Google Scholar), and R. J. 1994; Full Text PDF PubMed Scopus Google Scholar), the autoinducing are processed and secreted by proteins of two a proteolytic domain the and an domain an transporter that the autoinducing peptide Mol. Microbiol. 1995; PubMed Scopus Google Mol. Microbiol. 1997; PubMed Scopus Google Scholar). These proteins are encoded by genes in the as that and the two component signal transduction These gene as that of theagr P2 We that AgrB is not with of the found in bacteria, and it not a It is possible that S. aureus a mechanism to an from found in We proposed the model for the processing of AgrD propeptide and the of the AIP in S. The propeptide is at two AgrD by of the N-terminal peptide be a proteolytic at the of the C-terminal peptide in a which would with the cysteine would be required for these It be by of the peptide with and would not be for on the of the AgrB functions and the of be required to it as a novel We Wright of for and and
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