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KMID : 0364820120480030180
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Korean Journal of Microbiology
2012 Volume.48 No. 3 p.180 ~ p.186
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Analysis of Amino Acid Residues Affecting the Activity of QscR, a Quorum Sensing Receptor of Pseudomonas aeruginosa
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Park Su-Jin
Kim Su-kyoung
Lee Joon-Hee
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Abstract
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Pseudomonas aeruginosa, a Gram-negative bacterium, is an ubiquitous and opportunistic human pathogen, which
expresses many virulence factors through quorum sensing (QS) regulation. QscR, one of the QS signal receptors of
P. aeruginosa, has unique features that make it possible to distinguish QscR from other QS receptors. In the present
study, we focused on amino acid residues responsible for such a broad signal specificity of QscR. Thus we
constructed mutant QscRs: QscRT72I, QscRR132M, and QscRT140I by substituting 72nd threonine, 132nd arginine, and
140th threonine residues with isoleucine, methionine, and isoleucine, respectively by site-directed mutagenesis.
When we examined the activity of these mutant QscRs, QscRR132M failed to respond to N-3-oxododecanoyl
homoserine lactone (3OC12-HSL), but QscRT72I and QscRT140I remained the ability to respond to 3OC12-HSL
despite much reduction of the sensitivity. When we treated a variety of acyl-HSLs with different structure, QscRT72I
and QscRT140I showed better responsiveness to N-decanoyl HSL (C10-HSL) or N-dodecanoyl HSL (C12-HSL) that
has no oxo-moiety at 3rd carbon of acyl group than to 3OC12-HSL, and QscRR132M showed no responsiveness to any
acyl-HSLs tested here. In addition, QscRT72I andQscRT140I were inhibited by 5f, a QscR inhibitor as similarly as wild
type QscR was. These results suggest that while the 130th arginine is crucial in both activity and acyl-HSL binding of
QscR, the 72nd and 140th threonines are important in the activity, but they are little responsible for the discrimination
of acyl-HSLs or competitive inhibitor.
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KEYWORD
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Pseudomonas aeruginosa, QscR, quorum sensing, quorum sensing receptor
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