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Specificity of Signal-Binding via Non-AHL LuxR-Type Receptors.

Brameyer S, Heermann R - PLoS ONE (2015)

Bottom Line: However, PluR and PauR both harbor substitutions in the conserved amino acid motif compared to that in AHL sensors, which appeared to be important for binding the corresponding signaling molecules.Here we analyze the role of the conserved amino acids in the signal-binding domain of these two non-AHL LuxR-type receptors for their role in signal perception.Our studies reveal that the conserved amino acid motif alone is essential but not solely responsible for ligand-binding.

View Article: PubMed Central - PubMed

Affiliation: Biozentrum, Bereich Mikrobiologie, Ludwig-Maximilians-Universität München, Martinsried/München, Germany.

ABSTRACT
Quorum sensing is a typical communication system among Gram-negative bacteria used to control group-coordinated behavior via small diffusible molecules dependent on cell number. The key components of a quorum sensing system are a LuxI-type synthase, producing acyl-homoserine lactones (AHLs) as signaling molecules, and a LuxR-type receptor that detects AHLs to control expression of specific target genes. Six conserved amino acids are present in the signal-binding domain of AHL-sensing LuxR-type proteins, which are important for ligand-binding and -specificity as well as shaping the ligand-binding pocket. However, many proteobacteria possess LuxR-type regulators without a cognate LuxI synthase, referred to as LuxR solos. The two LuxR solos PluR and PauR from Photorhabdus luminescens and Photorhabdus asymbiotica, respectively, do not sense AHLs. Instead PluR and PauR sense alpha-pyrones and dialkylresorcinols, respectively, and are part of cell-cell communication systems contributing to the overall virulence of these Photorhabdus species. However, PluR and PauR both harbor substitutions in the conserved amino acid motif compared to that in AHL sensors, which appeared to be important for binding the corresponding signaling molecules. Here we analyze the role of the conserved amino acids in the signal-binding domain of these two non-AHL LuxR-type receptors for their role in signal perception. Our studies reveal that the conserved amino acid motif alone is essential but not solely responsible for ligand-binding.

No MeSH data available.


Related in: MedlinePlus

The TYDQYI-motif in the SBD of PauR is essential for the overall functionality of the receptor and DAR-sensing.The most drastic effects on DAR-sensing were gained with the replacement of S38A, T62A, Y66A, D75A and D75N in the SBD of PauR and a decreased effect on DAR-sensing were gained with the replacement of Y90C and I113S in PauR (lower right quadrant). The PauR derivatives Y40A, Y40F, D75E and Q76A dramatically influenced the structure of PauR and decrease its ability to bind and activate pcfAP.a. promoter (lower left quadrant). The activity of pcfAP.a. promoter was measured via luminescence as read-out and pictured values were taken 2 h after addition of 0.1% arabinose (lower axis) or 3.5 nM DAR (left axis) and compared to PauR wild type, which values were set to 100% (upper right quadrant). To evaluate the different derivatives, a cut-off of 70% was set for each value. RLU (relative light units) values for all PauR derivatives and PauR wild type are depicted in S4 Table.
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pone.0124093.g004: The TYDQYI-motif in the SBD of PauR is essential for the overall functionality of the receptor and DAR-sensing.The most drastic effects on DAR-sensing were gained with the replacement of S38A, T62A, Y66A, D75A and D75N in the SBD of PauR and a decreased effect on DAR-sensing were gained with the replacement of Y90C and I113S in PauR (lower right quadrant). The PauR derivatives Y40A, Y40F, D75E and Q76A dramatically influenced the structure of PauR and decrease its ability to bind and activate pcfAP.a. promoter (lower left quadrant). The activity of pcfAP.a. promoter was measured via luminescence as read-out and pictured values were taken 2 h after addition of 0.1% arabinose (lower axis) or 3.5 nM DAR (left axis) and compared to PauR wild type, which values were set to 100% (upper right quadrant). To evaluate the different derivatives, a cut-off of 70% was set for each value. RLU (relative light units) values for all PauR derivatives and PauR wild type are depicted in S4 Table.

Mentions: Amino acid substitutions in PluR or PauR might affect the spatial structure of the proteins and influence their functionality to bind the cognate pcfA promoter. To quantify the structural influence of amino acid replacements in the signal-binding domain (SBD) of PluR or PauR, the ability of PluR wild type or PauR wild type and different derivatives to activate pcfA promoter activity was determined. Therefore, the similar method was used as described above, however 0.1% (w/v) arabinose was added and also derivatives of PluR or PauR were used. For better comparison, the values of PluR wild type or PauR wild type was set as 100% in the Figs 3 and 4.


Specificity of Signal-Binding via Non-AHL LuxR-Type Receptors.

Brameyer S, Heermann R - PLoS ONE (2015)

The TYDQYI-motif in the SBD of PauR is essential for the overall functionality of the receptor and DAR-sensing.The most drastic effects on DAR-sensing were gained with the replacement of S38A, T62A, Y66A, D75A and D75N in the SBD of PauR and a decreased effect on DAR-sensing were gained with the replacement of Y90C and I113S in PauR (lower right quadrant). The PauR derivatives Y40A, Y40F, D75E and Q76A dramatically influenced the structure of PauR and decrease its ability to bind and activate pcfAP.a. promoter (lower left quadrant). The activity of pcfAP.a. promoter was measured via luminescence as read-out and pictured values were taken 2 h after addition of 0.1% arabinose (lower axis) or 3.5 nM DAR (left axis) and compared to PauR wild type, which values were set to 100% (upper right quadrant). To evaluate the different derivatives, a cut-off of 70% was set for each value. RLU (relative light units) values for all PauR derivatives and PauR wild type are depicted in S4 Table.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4414361&req=5

pone.0124093.g004: The TYDQYI-motif in the SBD of PauR is essential for the overall functionality of the receptor and DAR-sensing.The most drastic effects on DAR-sensing were gained with the replacement of S38A, T62A, Y66A, D75A and D75N in the SBD of PauR and a decreased effect on DAR-sensing were gained with the replacement of Y90C and I113S in PauR (lower right quadrant). The PauR derivatives Y40A, Y40F, D75E and Q76A dramatically influenced the structure of PauR and decrease its ability to bind and activate pcfAP.a. promoter (lower left quadrant). The activity of pcfAP.a. promoter was measured via luminescence as read-out and pictured values were taken 2 h after addition of 0.1% arabinose (lower axis) or 3.5 nM DAR (left axis) and compared to PauR wild type, which values were set to 100% (upper right quadrant). To evaluate the different derivatives, a cut-off of 70% was set for each value. RLU (relative light units) values for all PauR derivatives and PauR wild type are depicted in S4 Table.
Mentions: Amino acid substitutions in PluR or PauR might affect the spatial structure of the proteins and influence their functionality to bind the cognate pcfA promoter. To quantify the structural influence of amino acid replacements in the signal-binding domain (SBD) of PluR or PauR, the ability of PluR wild type or PauR wild type and different derivatives to activate pcfA promoter activity was determined. Therefore, the similar method was used as described above, however 0.1% (w/v) arabinose was added and also derivatives of PluR or PauR were used. For better comparison, the values of PluR wild type or PauR wild type was set as 100% in the Figs 3 and 4.

Bottom Line: However, PluR and PauR both harbor substitutions in the conserved amino acid motif compared to that in AHL sensors, which appeared to be important for binding the corresponding signaling molecules.Here we analyze the role of the conserved amino acids in the signal-binding domain of these two non-AHL LuxR-type receptors for their role in signal perception.Our studies reveal that the conserved amino acid motif alone is essential but not solely responsible for ligand-binding.

View Article: PubMed Central - PubMed

Affiliation: Biozentrum, Bereich Mikrobiologie, Ludwig-Maximilians-Universität München, Martinsried/München, Germany.

ABSTRACT
Quorum sensing is a typical communication system among Gram-negative bacteria used to control group-coordinated behavior via small diffusible molecules dependent on cell number. The key components of a quorum sensing system are a LuxI-type synthase, producing acyl-homoserine lactones (AHLs) as signaling molecules, and a LuxR-type receptor that detects AHLs to control expression of specific target genes. Six conserved amino acids are present in the signal-binding domain of AHL-sensing LuxR-type proteins, which are important for ligand-binding and -specificity as well as shaping the ligand-binding pocket. However, many proteobacteria possess LuxR-type regulators without a cognate LuxI synthase, referred to as LuxR solos. The two LuxR solos PluR and PauR from Photorhabdus luminescens and Photorhabdus asymbiotica, respectively, do not sense AHLs. Instead PluR and PauR sense alpha-pyrones and dialkylresorcinols, respectively, and are part of cell-cell communication systems contributing to the overall virulence of these Photorhabdus species. However, PluR and PauR both harbor substitutions in the conserved amino acid motif compared to that in AHL sensors, which appeared to be important for binding the corresponding signaling molecules. Here we analyze the role of the conserved amino acids in the signal-binding domain of these two non-AHL LuxR-type receptors for their role in signal perception. Our studies reveal that the conserved amino acid motif alone is essential but not solely responsible for ligand-binding.

No MeSH data available.


Related in: MedlinePlus