Conjugal plasmid transfer in Streptomyces resembles bacterial chromosome segregation by FtsK/SpoIIIE

• Published in: The EMBO journal 2011-06, Vol.30 (11), p.2246-2254
• Main Authors: Vogelmann, Jutta, Ammelburg, Moritz, Finger, Constanze, Guezguez, Jamil, Linke, Dirk, Flötenmeyer, Matthias, Stierhof, York-Dieter, Wohlleben, Wolfgang, Muth, Günther
• Format: Article
• Language: English
• Subjects: Bacteria; Bacterial Proteins - metabolism; Binding Sites; Chromosome Segregation; Chromosomes, Bacterial - genetics; conjugation; Conjugation, Genetic; conjugative DNA transfer; Deoxyribonucleic acid; DNA; DNA - metabolism; DNA, Bacterial - metabolism; EMBO13; EMBO20; Evolution, Molecular; FtsK; Gene Transfer, Horizontal; Genomes; Molecular biology; Phylogeny; Plasmids; Pores; Protein Binding; Protein Multimerization; Proteins; Sequence Analysis, DNA; Sequence Homology, Amino Acid; SpoIIIE; Streptomyces; Streptomyces coelicolor - genetics; TraB
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/emboj.2011.121

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. Most bacteria share virulence and resistance genes by transferring single‐stranded DNA through a type IV secretion system. Streptomycetes, however, exchange dsDNA, using a system found to closely resemble machineries for prokaryotic chromosome segregation or DNA translocation during spore formation.