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The bacterial conjugation protein TrwB resembles ring helicases and F1-ATPase


The transfer of DNA across membranes and between cells is a central biological process; however, its molecular mechanism remains unknown. In prokaryotes, trans-membrane passage by bacterial conjugation, is the main route for horizontal gene transfer. It is the means for rapid acquisition of new genetic information, including antibiotic resistance by pathogens. Trans-kingdom gene transfer from bacteria to plants1 or fungi2 and even bacterial sporulation3 are special cases of conjugation. An integral membrane DNA-binding protein, called TrwB in the Escherichia coli R388 conjugative system, is essential for the conjugation process. This large multimeric protein is responsible for recruiting the relaxosome DNA–protein complex, and participates in the transfer of a single DNA strand during cell mating. Here we report the three-dimensional structure of a soluble variant of TrwB. The molecule consists of two domains: a nucleotide-binding domain of α/β topology, reminiscent of RecA and DNA ring helicases, and an all-α domain. Six equivalent protein monomers associate to form an almost spherical quaternary structure that is strikingly similar to F1-ATPase. A central channel, 20 Å in width, traverses the hexamer.

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Figure 1: Structural features of TrwB.
Figure 2: Electrostatic surface representations.


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We are most grateful to R. Huber for making tantalum bromide available to us, and to I. Usón for help with SHELX. This work was supported by grants from the Ministerio de Educación y Cultura of Spain, the Generalitat de Catalunya and the European Union. Synchrotron data collection was supported by EU grants and the ESRF.

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Correspondence to Miquel Coll.

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Gomis-Rüth, F., Moncalián, G., Pérez-Luque, R. et al. The bacterial conjugation protein TrwB resembles ring helicases and F1-ATPase. Nature 409, 637–641 (2001).

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