This document discusses quorum sensing mechanisms in gram negative and gram positive bacteria. It specifically focuses on the LuxR 'solo' receptor found in Escherichia coli and analyzes the receptor-signal molecule interactions through structural analysis of various bacteria species including Chromobacterium violaceum, Pseudomonas aeruginosa, Escherichia coli, and Agrobacterium tumefaciens. The summary identifies conserved amino acid residues in the ligand binding sites of these receptors and notes common features such as the ligand binding domain, DNA binding domain, and interactions through hydrophobic pockets and hydrogen bonds.

1. Deciphering the QS
Mechanism: Structural
Analysis
Sahana.V
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2. Quorum Sensing: The basic mechanism
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Gram Negative
Passive Diffusion
Gram Positive
Two component regulated

3. LuxR ‘solo’ receptor
3/12Subromoni and Venturi,2009

4. Escherichia coli and its ‘solo’ receptor
• SdiA – Role in E.coli is not completely understood.
• Increases transcription of the cell division operon ftsQAZ
• Increases resistance to certain antibiotics and quinolones, probably
through activation of efflux pumps
• E. coli – activates Salmonella and E. coli gene promoters in an AHL
dependent manner
• Monitor strains :
• Pseudomonas fluorescens (produces N-octanoylL-homoserine lactone)
• Pseudomonas syringae (produces N-hexanoyl-L-homoserine lactone)
• Pseudomonas aeruginosa (produces N-butyryl-L-homoserine lactone)
Ahmer, 2004; Rahmati et al., 2002; Sitnikov et al., 1996 4/12

5. Interactions: Receptor and
Signal Molecule
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6. Receptor: Its Role
Guozhou Chen et al., 2011 6/12

7. 7

8. 8

9. Chromobacterium violecium
Guozhou Chen et al., 2011 9/12

10. • PDB ID: 3QP2
• Ligand: C8 HSL
• Binding Site:
• Tyr-80, Trp-84, Asp-97, Ser-155 [Conserved]
• PDB ID: 3QP1
• Ligand: C6 HSL
• Binding Site:
• Tyr-80, Trp-84, Asp-97, Ser-155[Conserved]
Guozhou Chen et al., 2011
Wallace A C, et al., 1996
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11. 11
Pseudomonas aeruginosa

12. Pseudomonas aeruginosa
• PDB ID: 2UV0
• Ligand: 3-oxo-C12 HSL
• Binding Site:
• Tyr-56, Trp-60, Asp-73, Ser-129 [Conserved]
Bottomleyet.al,2011
Wallace A C, et al., 1996
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13. 13
Escherichia coli

14. Escherichia coli
• PDB ID: 4Y17
• Ligand: C6- HSL
• Binding Site:
• Trp-67, Asp-80, Ser-43 [Conserved]
Y Nguyen et al.,2015
Truc Kim et al., 2013
Wallace A C, et al., 1996
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15. 15
Agrobacterium tumefaciens

16. Agrobacterium tumefaciens
• PDB ID: 1H0M
• Ligand: 3-oxo-C8 AHL
• Binding Site:
• Tyr-57, Asp-70 [Conserved]Vannini et al.,2002
Wallace A C, et al., 1996
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17. Common Points
1. Ligand
Binding
Domain
2. DNA
Binding
Domain
Domains
Tyrosine
Tryptophan
Aspartic
Acid
Serine
Binding Site
Hydrophobic
Pocket
Hydrogen
Bonds
Environment
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