title: Conjugal plasmid transfer in Streptomyces resembles bacterial chromosome segregation by FtsK/SpoIIIE.
abstract: Conjugation is a major route of horizontal gene transfer, the driving force in the evolution of bacterial genomes. Antibiotic producing soil bacteria of the genus Streptomyces transfer DNA in a unique process involving a single plasmid-encoded protein TraB and a double-stranded DNA molecule. However, the molecular function of TraB in directing DNA transfer from a donor into a recipient cell is unknown. Here, we show that TraB constitutes a novel conjugation system that is clearly distinguished from DNA transfer by a type IV secretion system. We demonstrate that TraB specifically recognizes and binds to repeated 8 bp motifs on the conjugative plasmid. The specific DNA recognition is mediated by helix α3 of the C-terminal winged-helix-turn-helix domain of TraB. We show that TraB assembles to a hexameric ring structure with a central ∼3.1 nm channel and forms pores in lipid bilayers. Structure, sequence similarity and DNA binding characteristics of TraB indicate that TraB is derived from an FtsK-like ancestor protein, suggesting that Streptomyces adapted the FtsK/SpoIIIE chromosome segregation system to transfer DNA between two distinct Streptomyces cells.
authors.affiliation: Interfakultaeres Institut für Mikrobiologie und Infektionsmedizin Tuebingen IMIT, Mikrobiologie/Biotechnologie, Eberhard Karls Universitaet Tuebingen, Tuebingen, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Vogelmann
authors.forename: Moritz
authors.initials: M
authors.lastname: Ammelburg
authors.forename: Constanze
authors.initials: C
authors.lastname: Finger
authors.forename: Jamil
authors.initials: J
authors.lastname: Guezguez
authors.forename: Dirk
authors.initials: D
authors.lastname: Linke
authors.forename: Matthias
authors.initials: M
authors.lastname: Flötenmeyer
authors.forename: York-Dieter
authors.initials: YD
authors.lastname: Stierhof
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wohlleben
authors.forename: Günther
authors.initials: G
authors.lastname: Muth
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D020090:Chromosome Segregation; D002876:Chromosomes, Bacterial / Q000235:genetics; D003227:Conjugation, Genetic; D004247:DNA / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D010802:Phylogeny; D010957:Plasmids; D011485:Protein Binding; D055503:Protein Multimerization; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D048372:Streptomyces coelicolor / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C082576:traB protein, Bacteria; D004247:DNA