title: A novel fold in the TraI relaxase-helicase c-terminal domain is essential for conjugative DNA transfer.
abstract: TraI relaxase-helicase is the central catalytic component of the multiprotein relaxosome complex responsible for conjugative DNA transfer (CDT) between bacterial cells. CDT is a primary mechanism for the lateral propagation of microbial genetic material, including the spread of antibiotic resistance genes. The 2.4-A resolution crystal structure of the C-terminal domain of the multifunctional Escherichia coli F (fertility) plasmid TraI protein is presented, and specific structural regions essential for CDT are identified. The crystal structure reveals a novel fold composed of a 28-residue N-terminal alpha-domain connected by a proline-rich loop to a compact alpha/beta-domain. Both the globular nature of the alpha/beta-domain and the presence as well as rigidity of the proline-rich loop are required for DNA transfer and single-stranded DNA binding. Taken together, these data establish the specific structural features of this noncatalytic domain that are essential to DNA conjugation.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, 27599-3290, USA.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Guogas
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Kennedy
authors.forename: Jin-Hyup
authors.initials: JH
authors.lastname: Lee
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Redinbo
mesh_terms: D000595:Amino Acid Sequence; D003227:Conjugation, Genetic; D018360:Crystallography, X-Ray; D004265:DNA Helicases / Q000737:chemistry* / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism*; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D022761:Gene Transfer, Horizontal; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C027093:TraI protein, E coli; D004265:DNA Helicases