title: Structural basis of cooperative DNA recognition by the plasmid conjugation factor, TraM.
abstract: The conjugative transfer of F-like plasmids such as F, R1, R100 and pED208, between bacterial cells requires TraM, a plasmid-encoded DNA-binding protein. TraM tetramers bridge the origin of transfer (oriT) to a key component of the conjugative pore, the coupling protein TraD. Here we show that TraM recognizes a high-affinity DNA-binding site, sbmA, as a cooperative dimer of tetramers. The crystal structure of the TraM-sbmA complex from the plasmid pED208 shows that binding cooperativity is mediated by DNA kinking and unwinding, without any direct contact between tetramers. Sequence-specific DNA recognition is carried out by TraM's N-terminal ribbon-helix-helix (RHH) domains, which bind DNA in a staggered arrangement. We demonstrate that both DNA-binding specificity, as well as selective interactions between TraM and the C-terminal tail of its cognate TraD mediate conjugation specificity within the F-like family of plasmids. The ability of TraM to cooperatively bind DNA without interaction between tetramers leaves the C-terminal TraM tetramerization domains free to make multiple interactions with TraD, driving recruitment of the plasmid to the conjugative pore.
authors.affiliation: Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada.
authors.forename: Joyce J W
authors.initials: JJ
authors.lastname: Wong
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
authors.forename: Ross A
authors.initials: RA
authors.lastname: Edwards
authors.forename: Laura S
authors.initials: LS
authors.lastname: Frost
authors.forename: J N Mark
authors.initials: JN
authors.lastname: Glover
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D004269:DNA, Bacterial / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005144:F Factor / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins