title: The bacterial conjugation protein TrwB resembles ring helicases and F1-ATPase.
abstract: 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.
authors.affiliation: Institut de Biologia Molecular de Barcelona, CSIC,  Spain.
authors.forename: F X
authors.initials: FX
authors.lastname: Gomis-Rüth
authors.forename: G
authors.initials: G
authors.lastname: Moncalián
authors.forename: R
authors.initials: R
authors.lastname: Pérez-Luque
authors.forename: A
authors.initials: A
authors.lastname: González
authors.forename: E
authors.initials: E
authors.lastname: Cabezón
authors.forename: F
authors.initials: F
authors.lastname: de la Cruz
authors.forename: M
authors.initials: M
authors.lastname: Coll
mesh_terms: 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
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C403125:trwB protein, E coli; D006180:Proton-Translocating ATPases; D004265:DNA Helicases