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Mol Microbiol

Title:		"TrlR, a defective TraR-like protein of Agrobacterium tumefaciens, blocks TraR function in vitro by forming inactive TrlR:TraR dimers"
Author(s):		Chai Y; Zhu J; Winans SC;
Address:		"Department of Microbiology, 360A Wing Hall, Cornell University, Ithaca, NY 4853, USA"
Journal Title:		Mol Microbiol
Year:		2001
Volume:		40
Issue:		2
Page Number:		414 - 421
DOI:		10.1046/j.1365-2958.2001.02385.x
ISSN/ISBN:		0950-382X (Print) 0950-382X (Linking)
Abstract:		"Octopine-type Ti plasmids of Agrobacterium tumefaciens require the quorum-sensing proteins TraR and TraI and the diffusible pheromone 3-oxooctanoyl homoserine lactone (AAI) to regulate genes required for conjugal transfer. TraR activity is inhibited by a protein called TrlR, which closely resembles amino acids 1-181 of TraR but is truncated as a result of a shift in the reading frame at codon 182. This frameshift does not affect synthesis of the amino-terminal domain, which is thought to bind autoinducer and mediate protein dimerization, but abolishes translation of the carboxyl-terminal, DNA-binding domain. In this study, we show that TrlR, like TraR, requires AAI for solubility when overexpressed in Escherichia coli. TrlR bound one molecule of AAI per protein monomer, supporting the prediction that the amino-terminal domain of TraR contains the AAI binding site. Purified TrlR blocked TraR for both specific DNA binding and transcription of a tra promoter, supporting previous studies performed with whole cells. When TrlR and a TraR fusion protein were co-expressed in E. coli, these proteins readily formed heterodimeric complexes that were inactive in DNA-binding activity. These data support the hypotheses that (i) the amino-terminal half of TraR binds AAI and mediates protein dimerization; (ii) both DNA-binding domains in a TraR dimer are required for stable DNA binding; and (iii) TrlR blocks TraR by direct protein-protein interactions"
Keywords:		"4-Butyrolactone/*analogs & derivatives/metabolism Agrobacterium tumefaciens/genetics/*metabolism Bacterial Proteins/chemistry/genetics/*metabolism DNA, Bacterial/metabolism Dimerization *Gene Expression Regulation, Bacterial Plasmids/genetics Transcriptio;"
Notes:		"MedlineChai, Y Zhu, J Winans, S C eng GM 42893/GM/NIGMS NIH HHS/ Research Support, U.S. Gov't, P.H.S. England 2001/04/20 Mol Microbiol. 2001 Apr; 40(2):414-21. doi: 10.1046/j.1365-2958.2001.02385.x"