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Updated: Aug 25, 2026

Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation
Published on: January 4, 2017
Crystal structure of the quorum-sensing protein TraM and its interaction with the transcriptional regulator TraR
Alessandro Vannini1, Cinzia Volpari, Stefania Di Marco
1Department of Biochemistry, Istituto di Ricerche di Biologia Molecolare Pietro Angeletti, 00040 Pomezia, Rome, Italy.
Abstract:
Transfer of the tumor-inducing plasmid in Agrobacterium tumefaciens is controlled by a quorum-sensing system whose main components are the transcriptional regulator TraR and its autoinducer. This system allows bacteria to synchronize infection of the host plant when a "quorum" of cells has been reached. TraM is an A. tumefaciens protein involved in the regulation of this system because it binds to TraR and prevents it from binding DNA. As a first step to understanding the molecular basis for the regulation of TraR by TraM, we have determined the crystal structure of TraM at 1.65 A resolution. This protein is packed as a dimer, with each monomer consisting mainly of two antiparallel alpha helices. Monomers are tightly associated, with a large hydrophobic area buried upon dimerization. Secondly, we characterized the TraR-TraM complex in vitro. TraM (11.4 kDa, monomer molecular mass) binds tightly TraR (27 kDa, monomer molecular mass) forming a stable oligomeric complex that likely accounts for two TraR and two TraM dimers.
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