Article
- The EMBO Journal (2000) 19, 5212 - 5221
- doi:10.1093/emboj/19.19.5212
Quorum-sensing signal binding results in dimerization of TraR and its release from membranes into the cytoplasm
Yinping Qin1, Zhao-Qing Luo1, Audra J. Smyth1, Ping Gao1, Susanne Beck von Bodman2 and Stephen K. Farrand1,3
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, 1201 West Gregory Drive Urbana, IL 61801 USA
- Department of Plant Sciences, University of Connecticut, Storrs, CT, USA
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA
Correspondence to:
Stephen K. Farrand, E-mail: stephenf@uiuc.edu
Received 14 June 2000; Accepted 7 August 2000; Revised 1 August 2000
Abstract
Promoter binding by TraR and LuxR, the activators of two bacterial quorum-sensing systems, requires their cognate acyl-homoserine lactone (acyl-HSL) signals, but the role the signal plays in activating these transcription factors is not known. Soluble active TraR, when purified from cells grown with the acyl-HSL, contained bound signal and was solely in dimer form. However, genetic and cross-linking studies showed that TraR is almost exclusively in monomer form in cells grown without signal. Adding signal resulted in dimerization of the protein in a concentration-dependent manner. In the absence of signal, monomer TraR localized to the inner membrane while growth with the acyl-HSL resulted in the appearance of dimer TraR in the cytoplasmic compartment. Affinity chromatography indicated that the N-terminus of TraR from cells grown without signal is hidden. Analysis of heterodimers formed between TraR and its deletion mutants localized the dimerization domain to a region between residues 49 and 156. We conclude that binding signal drives dimerization of TraR and its release from membranes into the cytoplasm.
Keywords:
- acyl-homoserine lactone,
- Agrobacterium tumefaciens,
- quorum sensing,
- Ti plasmid,
- TraR dimerization
