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Analysis of Amino Acid Residues Affecting the Activity of QscR, a Quorum Sensing Receptor of Pseudomonas aeruginosa

녹농균(Pseudomonas aeruginosa)의 쿼럼 센싱 수용체인 QscR의 활성에 영향을 미치는 아미노산 잔기 분석

  • Park, Su-Jin (Department of Pharmacy, College of Pharmacy, Pusan National University) ;
  • Kim, Soo-Kyoung (Department of Pharmacy, College of Pharmacy, Pusan National University) ;
  • Lee, Joon-Hee (Department of Pharmacy, College of Pharmacy, Pusan National University)
  • 박수진 (부산대학교 약학대학 약학과 미생물학 연구실) ;
  • 김수경 (부산대학교 약학대학 약학과 미생물학 연구실) ;
  • 이준희 (부산대학교 약학대학 약학과 미생물학 연구실)
  • Received : 2012.08.31
  • Accepted : 2012.09.12
  • Published : 2012.09.30

Abstract

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: $QscR_{T72I}$, $QscR_{R132M}$, and $QscR_{T140I}$ by substituting $72^{nd}$ threonine, $132^{nd}$ arginine, and $140^{th}$ threonine residues with isoleucine, methionine, and isoleucine, respectively by site-directed mutagenesis. When we examined the activity of these mutant QscRs, $QscR_{R132M}$ failed to respond to N-3-oxododecanoyl homoserine lactone (3OC12-HSL), but $QscR_{T72I}$ and $QscR_{T140I}$ 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, $QscR_{T72I}$ and $QscR_{T140I}$ showed better responsiveness to N-decanoyl HSL (C10-HSL) or N-dodecanoyl HSL (C12-HSL) that has no oxo-moiety at $3^{rd}$ carbon of acyl group than to 3OC12-HSL, and $QscR_{R132M}$ showed no responsiveness to any acyl-HSLs tested here. In addition, $QscR_{T72I}$ and $QscR_{T140I}$ were inhibited by 5f, a QscR inhibitor as similarly as wild type QscR was. These results suggest that while the $130^{th}$ arginine is crucial in both activity and acyl-HSL binding of QscR, the $72^{nd}$ and $140^{th}$ threonines are important in the activity, but they are little responsible for the discrimination of acyl-HSLs or competitive inhibitor.

Keywords

Pseudomonas aeruginosa;QscR;quorum sensing;quorum sensing receptor

Acknowledgement

Supported by : 부산대학교

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