PROSITE documentation PDOC00731
Autoinducer synthase family signature and profile


Autoinducers are hormone-like molecules produced by bacteria as signals to sense cell density and activate adaptations, by a process termed quorum sensing. N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) is a molecule produced by a number of Gram-negative bacteria that acts as an autoinducer by binding to transcriptional regulatory proteins and activating them [1,2]. OHHL and related molecules such as N-butanoyl- (BHL), N-hexanoyl- (HHL) and N-oxododecanoyl- (PAI) homoserine lactones are produced by a family of proteins which have a length of about 200 amino acids. The 3D structures of autoinducer synthases (see <PDB:1KZF>) have features essential for phosphopantetheine binding and N-acylation that are similar to that of Gcn5-related N-acetyltransferases (GNAT) (see <PDOC51186>) [3,4].

Some proteins currently known to belong to the autoinducer synthase family:

  • Vibrio fischeri luxI. The target of OHHL is the luxR protein that acts in the regulation of bioluminescence genes.
  • Aeromonas ahyI and asaI, which synthesize BHL and whereof the targets are ahyR and asaR.
  • Agrobacterium tumefaciens traI. The target of OHHL is traR which regulates Ti plasmid transfer.
  • Erwinia carotovora carI. The target of OHHL is carR which activates genes involved in the biosynthesis of carbapenem antibiotics.
  • Erwinia carotovora expI. The target of OHHL is expR which is involved in virulence (soft rot disease) by activating the genes for plant tissue macerating enzymes.
  • Erwinia stewartii esaI. The target of OHHL is esaR which is involved in the regulation of the biosynthesis of EPS virulence factor.
  • Pseudomonas aeruginosa lasI, which synthesizes PAI and whose target is lasR which activates the transcription of the elastase gene.
  • Pseudomonas aureofaciens phzI, whose target is phzR, the activator of phenazine biosynthetic genes.
  • Pseudomonas aeruginosa rhlI (or vsmI), which synthesizes BHL and HHL and whose target is rhlR.
  • Serratia liquefaciens swrI, which synthesizes BHL.
  • Enterobacter agglomerans eagI.
  • Yersinia enterocolitica yenI.

The best conserved region is located in the N-terminal region and can be used as a signature pattern. We also developed a profile which covers the entire autoinducer synthase domain.

Last update:

March 2006 / Text revised; profile added.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

AUTOINDUCER_SYNTH_2, PS51187; Autoinducer synthase family profile  (MATRIX)

AUTOINDUCER_SYNTH_1, PS00949; Autoinducer synthase family signature  (PATTERN)


1AuthorsSwift S. Winson M.K. Chan P.F. Bainton N.J. Birdsall M. Reeves P.J. Rees C.E.D. Chhabra S.R. Hill P.J. Throup J.P. Bycroft B.W. Salmond G.P.C. Williams P. Stewart G.S.A.B.
TitleA novel strategy for the isolation of luxI homologues: evidence for the widespread distribution of a LuxR:LuxI superfamily in enteric bacteria.
SourceMol. Microbiol. 10:511-520(1993).
PubMed ID7968529

2AuthorsLatifi A. Winson M.K. Foglino M. Bycroft B.W. Stewart G.S.A.B. Lazdunski A. Williams P.
TitleMultiple homologues of LuxR and LuxI control expression of virulence determinants and secondary metabolites through quorum sensing in Pseudomonas aeruginosa PAO1.
SourceMol. Microbiol. 17:333-343(1995).
PubMed ID7494482

3AuthorsWatson W.T. Minogue T.D. Val D.L. von Bodman S.B. Churchill M.E.
TitleStructural basis and specificity of acyl-homoserine lactone signal production in bacterial quorum sensing.
SourceMol. Cell 9:685-694(2002).
PubMed ID11931774

4AuthorsGould T.A. Schweizer H.P. Churchill M.E.
TitleStructure of the Pseudomonas aeruginosa acyl-homoserinelactone synthase LasI.
SourceMol. Microbiol. 53:1135-1146(2004).
PubMed ID15306017

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