Membrane anchoring of the AgrD N-terminal amphipathic region is required for its processing to produce a quorum-sensing pheromone in Staphylococcus aureus.
Quorum-sensing pheromones are signal molecules that are secreted from Gram-positive bacteria and utilized by these bacteria to communicate among individual cells to regulate their activities as a group through a cell density-sensing mechanism. Typically, these pheromones are processed from precursor polypeptides. The mechanisms of trafficking, processing, and modification of the precursor to generate a mature pheromone are unclear. In Staphylococcus aureus, AgrD is the propeptide for an autoinducing peptide (AIP) pheromone that triggers the Agr cell density-sensing system upon reaching a threshold and subsequently regulates expression of virulence factor genes. The transmembrane protein AgrB, encoded in the agr locus, is necessary for the processing of AgrD to produce mature AIP; however, it is not clear how AgrD interacts with AgrB and how this interaction results in the generation of mature AIP. In this study, we found that the AgrD propeptide was integrated into the cytoplasmic membrane by a conserved alpha-helical amphipathic motif in its N-terminal region. We demonstrated that membrane targeting of AgrD by this motif was required for the stabilization of AgrD and the production of mature AIP, although this region was not specifically involved in the interaction with AgrB. An artificial amphipathic peptide replacing the N-terminal amphipathic motif of AgrD directed the protein to the cytoplasmic membrane and enabled the production of AIP. Analysis of Bacillus ComX precursor protein sequences suggested that the amphipathic membrane-targeting motif might also exist in pheromone precursors of other Gram-positive bacteria.
Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
Linsheng
L
Zhang
Jianqun
J
Lin
Guangyong
G
Ji
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D017353:Gene Deletion; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D010456:Peptides, Cyclic; D010675:Pheromones / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013211:Staphylococcus aureus / Q000378:metabolism*; D013347:Subcellular Fractions
C414533:AgrB protein, Staphylococcus aureus; C414532:AgrD protein, Staphylococcus; D001426:Bacterial Proteins; C087040:ComX protein, Bacillus subtilis; D010456:Peptides, Cyclic; D010675:Pheromones; D011993:Recombinant Fusion Proteins