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 plants or fungi and even bacterial sporulation 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 alpha/beta topology, reminiscent of RecA and DNA ring helicases, and an all-alpha domain. Six equivalent protein monomers associate to form an almost spherical quaternary structure that is strikingly similar to F1-ATPase. A central channel, 20 A in width, traverses the hexamer.
Gomis-Rüth
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Institut de Biologia Molecular de Barcelona, CSIC,  Spain.
Moncalián
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G
Pérez-Luque
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González
A
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Cabezón
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E
de la Cruz
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F
Coll
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D001426:Bacterial Proteins / Q000737:chemistry; D003227:Conjugation, Genetic; D018360:Crystallography, X-Ray; D004265:DNA Helicases / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000737:chemistry
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C403125:trwB protein, E coli; D006180:Proton-Translocating ATPases; D004265:DNA Helicases