title: Rhomboid protease AarA mediates quorum-sensing in Providencia stuartii by activating TatA of the twin-arginine translocase.
abstract: The Providencia stuartii AarA protein is a member of the rhomboid family of intramembrane serine proteases and is required for the production of an unknown quorum-sensing molecule. In a screen to identify rhomboid-encoding genes from Proteus mirabilis, tatA was identified as a multicopy suppressor and restored extracellular signal production as well as complementing all other phenotypes of a Prov. stuartii aarA mutant. TatA is a component of the twin-arginine translocase (Tat) protein secretion pathway and likely forms a secretion pore. By contrast, the native tatA gene of Prov. stuartii in multicopy did not suppress an aarA mutation. We find that TatA in Prov. stuartii has a short N-terminal extension that was atypical of TatA proteins from most other bacteria. This extension was proteolytically removed by AarA both in vivo and in vitro. A Prov. stuartii TatA protein missing the first 7 aa restored the ability to rescue the aarA-dependent phenotypes. To verify that loss of the Tat system was responsible for the various phenotypes exhibited by an aarA mutant, a tatC-null allele was constructed. The tatC mutant exhibited the same phenotypes as an aarA mutant and was epistatic to aarA. These data provide a molecular explanation for the requirement of AarA in quorum-sensing and uncover a function for the Tat protein export system in the production of secreted signaling molecules. Finally, TatA represents a validated natural substrate for a prokaryotic rhomboid protease.
authors.affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA 30322, USA.
authors.forename: Lindsay G
authors.initials: LG
authors.lastname: Stevenson
authors.forename: Kvido
authors.initials: K
authors.lastname: Strisovsky
authors.forename: Katy M
authors.initials: KM
authors.lastname: Clemmer
authors.forename: Shantanu
authors.initials: S
authors.lastname: Bhatt
authors.forename: Matthew
authors.initials: M
authors.lastname: Freeman
authors.forename: Philip N
authors.initials: PN
authors.lastname: Rather
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001692:Biological Transport; D004789:Enzyme Activation; D018628:Gene Dosage; D015870:Gene Expression; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009876:Operon / Q000235:genetics; D010641:Phenotype; D011532:Providencia / Q000201:enzymology* / Q000235:genetics; D053038:Quorum Sensing; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D012097:Repressor Proteins; C088713:aarA protein, Providencia stuartii