Rhomboid Protease AarA Mediates Quorum-Sensing in Providencia stuartii by Activating TatA of the Twin-Arginine Translocase

• Published in: Proceedings of the National Academy of Sciences - PNAS 2007-01, Vol.104 (3), p.1003-1008
• Main Authors: Stevenson, Lindsay G., Strisovsky, Kvido, Clemmer, Katy M., Bhatt, Shantanu, Freeman, Matthew, Rather, Philip N.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Amino Acids - genetics; Amino Acids - metabolism; Bacterial proteins; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - isolation & purification; Bacterial Proteins - metabolism; Biological Sciences; Biological Transport; Cell growth; Enzyme Activation; Enzymes; Gene Dosage; Gene Expression; Genetic mutation; Genotype & phenotype; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Molecular biology; Molecular Sequence Data; Molecules; Mutation; Mutation - genetics; Operon - genetics; Operons; Phenotype; Phenotypes; Pigments; Plasmids; Proteins; Proteus mirabilis; Providencia - enzymology; Providencia - genetics; Providencia stuartii; Quorum Sensing; Repressor Proteins - chemistry; Repressor Proteins - genetics; Repressor Proteins - isolation & purification; Repressor Proteins - metabolism; Sequence Alignment; Signal Transduction
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0608140104

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.