Deciphering the QS Mechanism: Structural

AnalysisSahana.V

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Quorum Sensing: The basic mechanism

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Gram Negative

Passive Diffusion

Gram Positive

Two component regulated

LuxR ‘solo’ receptor

3/12Subromoni and Venturi,2009

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

Interactions: Receptor and Signal Molecule

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Receptor: Its Role

Guozhou Chen et al., 2011

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7

8

Chromobacterium violecium

Guozhou Chen et al., 2011

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• 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

Pseudomonas aeruginosa

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

Escherichia coli

Escherichia coli

• PDB ID: 4Y17• Ligand: C6- HSL• Binding Site:

• Trp-67, Asp-80, Ser-43 [Conserved]Y Nguyen et al.,2015Truc Kim et al., 2013

Wallace A C, et al., 1996

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15

Agrobacterium tumefaciens

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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Common Points1. Ligand Binding Domain2. DNA Binding Domain

Domains

TyrosineTryptophanAspartic AcidSerine

Binding Site

Hydrophobic PocketHydrogen Bonds

Environment

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