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Lsr (AI-2) cell signaling system

Responsible: Kelly Davis, Xiao Zhu

Signal molecule: AI-2 (furanosyl borate diester in V. harveyi, a variety of other molecules in other species), all are derived from DPD. AI-2 is R-THMF in E. coli


Bacterial species:

lsrA,B,C,D,F,G,R,K: Escherichia coli HS, SMS-3-5, str. K12 substr. MG1655, and substr. DH10B.

lsrE:Escherichia coli str. K12 substr. MG1655

LuxS:Escherichia coli HS, SMS-3-5, APEC O1, str. K12 substr. MG1655, substr. DH10B, and UTI89.

Receiver protein: LsrR protein receives signal from sensor protein

Signal molecule synthase: Pfs enzyme, then LuxS autoinducer synthase

Target genes: lsr operon, including ABC transporter and LsrK kinase

Regulation: LsrR represses the lsr operon, derepression by phospho-AI-2; catabolite repression influences AI-2 accumulation through the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex, which directly stimulates transcription of the lsr operon and indirectly represses luxS expression.cAMP-CRP is shown to bind to a cAMP receptor protein (CRP) binding site located in the upstream region of the lsr promoter and works with the LsrR repressor to regulate AI-2 uptake.

Note: AI-2 is synthesized and secreted during exponential growth and is imported in stationary phase when glucose becomes limiting. In the presence of glucose, AI-2 is not imported because the lsr operon is not transcribed due to camp-CAP mediated repression. Both glycerol and G3P(glycerol 3-phosphate) repress lsr transcription, while the majority repression comes from G3P. DHAP represses lsr transcription by a cAMP-CAP-independent mechanism involving LsrR.

Parts Needed:

LsrR pro/term


LsrACDB (transport)

LsrFGE (catabolic)


Pfs enzyme (?)


lsrB encodes the periplasmic AI-2 binding protein

lsrC & lsrD encode the channel proteins

lsrA encodes the ATPase that provides energy for AI-2 transport

lsrF is similar to genes specifying aldolases

lsrG encodes a protein with an unknown function.

tam: trans-aconitate 2-methyltransferase, also known as lsrE or yneD yneE:conserved inner membrane protein


DHAP: dihydroxyacetone phosphate.


Cyclic AMP and cAMP Receptor Protein Influence both Synthesis and Uptake of Extracellular Autoinducer 2 in Escherichia coli

Global Effects of the Cell-to-Cell Signaling Molecules Autoinducer-2, Autoinducer-3, and Epinephrine in a luxS Mutant of Enterohemorrhagic Escherichia Coli

Shows how AI-2 is formed

Signaling explained with graphics of AI-2 pathways

Lsr-mediated transport and processing of AI-2 in Salmonella typhimurium

Review of AI-2 and other systems

Quorum Sensing in Escherichia coli Is Signaled by AI-2/LsrR: Effects on Small RNA and Biofilm Architecture

Regulation of Uptake and Processing of the Quorum-Sensing Autoinducer AI-2 in Escherichia coli



alternate AI-2 synthesis

lsrK gene in Entrez

lsrR gene in Entrez

lsr nucleotide sequence in EcoCyc

Transcription of LuxS (interaction with micA,gshA)