Structure of TrwB, a gatekeeper in bacterial conjugation.
Bacterial conjugation implies a trans-membrane passage of DNA, mediated by proteins encoded in conjugative plasmids. This results in a spread of genetic information, including antibiotic resistance acquisition by pathogens. Special cases of conjugation are trans-kingdom gene transfer from bacteria to plants or fungi, and even bacterial sporulation and cell division. One of the main actors in this process is an integral inner membrane DNA-binding protein, called TrwB in the E. coli R388 conjugative system. It is responsible for coupling the single-strand DNA to be transferred from the donor to the acceptor cell in its complex with other proteins, with a type IV secretion system making up the mating apparatus. The TrwB protomer consists of two domains: a nucleotide-binding domain of alpha/beta topology, similar to RecA and DNA ring helicases, and an all-alpha domain. The quaternary structure reveals an almost spherical homohexamer, strikingly similar to F(1)-ATPase. A central 20 A wide channel traverses the hexamer, thus connecting cytoplasm with periplasm.
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Institut de Biologia Molecular de Barcelona, C.S.I.C., c/Jordi Girona, 18-26, 08034 Barcelona, Spain. xgrcri@ibmb.csic.es
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D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D002462:Cell Membrane / Q000648:ultrastructure; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C403125:trwB protein, E coli