title: TraG-like proteins of DNA transfer systems and of the Helicobacter pylori type IV secretion system: inner membrane gate for exported substrates?
abstract: TraG-like proteins are potential NTP hydrolases (NTPases) that are essential for DNA transfer in bacterial conjugation. They are thought to mediate interactions between the DNA-processing (Dtr) and the mating pair formation (Mpf) systems. TraG-like proteins also function as essential components of type IV secretion systems of several bacterial pathogens such as Helicobacter pylori. Here we present the biochemical characterization of three members of the family of TraG-like proteins, TraG (RP4), TraD (F), and HP0524 (H. pylori). These proteins were found to have a pronounced tendency to form oligomers and were shown to bind DNA without sequence specificity. Standard NTPase assays indicated that these TraG-like proteins do not possess postulated NTP-hydrolyzing activity. Surface plasmon resonance was used to demonstrate an interaction between TraG and relaxase TraI of RP4. Topology analysis of TraG revealed that TraG is a transmembrane protein with cytosolic N and C termini and a short periplasmic domain close to the N terminus. We predict that multimeric inner membrane protein TraG forms a pore. A model suggesting that the relaxosome binds to the TraG pore via TraG-DNA and TraG-TraI interactions is presented.
authors.affiliation: Max-Planck-Institut für Molekulare Genetik, Abteilung Lehrach, Ihnestrasse 73, Dahlem, D-14195 Berlin, Germany.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Schröder
authors.forename: Sabine
authors.initials: S
authors.lastname: Krause
authors.forename: Ellen L
authors.initials: EL
authors.lastname: Zechner
authors.forename: Beth
authors.initials: B
authors.lastname: Traxler
authors.forename: Hye-Jeong
authors.initials: HJ
authors.lastname: Yeo
authors.forename: Rudi
authors.initials: R
authors.lastname: Lurz
authors.forename: Gabriel
authors.initials: G
authors.lastname: Waksman
authors.forename: Erich
authors.initials: E
authors.lastname: Lanka
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D001692:Biological Transport; D003227:Conjugation, Genetic; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism; D029968:Escherichia coli Proteins; D016480:Helicobacter pylori / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D043583:Nucleoside-Triphosphatase
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C073791:TraG protein, E coli; D004247:DNA; D017766:Acid Anhydride Hydrolases; C027093:TraI protein, E coli; D043583:Nucleoside-Triphosphatase; D004265:DNA Helicases