This Article Full Text (PDF) Other Versions of this Article: JB.00954-06v1 188/23/8244    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chen, G. Articles by Chen, L. Search for Related Content PubMed PubMed Citation Articles by Chen, G. Articles by Chen, L.

 Previous Article  |  Next Article 

J. Bacteriol. doi:10.1128/JB.00954-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The Crystal Structure and Mechanism of TraM2, a Second Quorum Sensing Antiactivator of Agrobacterium tumefaciens strain A6

Department of Biology, 915 E. 3^rd St., Indiana University, Bloomington, IN 47405; Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673

^* To whom correspondence should be addressed. Email: linchen{at}indiana.edu.

	Abstract

Quorum sensing is a community behavior that bacteria utilize to coordinate a variety of population-density-dependent biological functions. In Agrobacterium tumefaciens quorum sensing regulates the replication and conjugative transfer of the tumor-inducing (Ti) plasmid from pathogenic strains to non-pathogenic derivatives. Most of the quorum-sensing regulatory proteins are encoded within Ti plasmid. Among these, TraR is a LuxR-type transcription factor playing a key role as the quorum-sensing signal receptor, and TraM is an anti-activator that antagonizes TraR through formation of a stable oligomeric complex. Recently a second TraM homologue called TraM2, not encoded on the Ti plasmid of A. tumefaciens A6 was identified, in addition to a copy on the Ti plasmid. In this report, we have characterized TraM2 and its interaction with TraR, and solved its crystal structure to 2.1 Å. Like TraM, TraM2 folds into a helical bundle, and exists as homodimer. TraM2 forms a stable complex (Kd = 8.6 nM) with TraR in a 1:1 binding ratio, a weaker affinity than TraM. Structural analysis and biochemical studies suggest that protein stability may account for the difference between TraM2 and TraM in their binding affinity to TraR, and provide a structural basis for L54 in promoting structural stability of TraM.

This article has been cited by other articles:

• Chen, G., Jeffrey, P. D., Fuqua, C., Shi, Y., Chen, L. (2007). Structural basis for antiactivation in bacterial quorum sensing. Proc. Natl. Acad. Sci. USA 104: 16474-16479 [Abstract] [Full Text]  
• Qin, Y., Su, S., Farrand, S. K. (2007). Molecular Basis of Transcriptional Antiactivation: TraM DISRUPTS THE TraR-DNA COMPLEX THROUGH STEPWISE INTERACTIONS. J. Biol. Chem. 282: 19979-19991 [Abstract] [Full Text]