A gene product related to Tral is required for the mobilization of Bacteroides mobilizable transposons and plasmids.
The antibiotic-resistance transposon Tn4555 from Bacteroides can be transferred between strains by conjugation. The transposon is not self-transmissible and must be mobilized by resident chromosomal tetracycline-resistance elements. In the present report, the mechanism of transfer was examined at the genetic level by deletion analysis and nucleotide sequencing of clones that conferred a transmissible phenotype on a non-mobilizable plasmid. The results suggested that the product of mobATn was required for mobilization and it worked in concert with a cis-acting oriT-like sequence. This mechanism was compared with the mobilization system of a cryptic Bacteroides plasmid, pBI143, and the two systems were found to share a common transfer strategy. The mobA gene products from both genetic elements were related and they had limited homology to the broad group of mobilization proteins (relaxases) typified by Tral of RP4. Phylogenetic analysis of MobA and several other mobilization proteins from commensal gastro-intestinal tract organisms suggested that they formed a new subgroup of the Tral superfamily. The mobilization regions of both Tn4555 and pBI143 were located on discrete segments of DNA within the parent genetic element. These segments were delineated by regions of secondary structure, suggesting that they could be defined mobilization cassettes.
Smith
C J
CJ
Department of Microbiology and Immunology, East Carolina University School of Medicine, Greenville, North Carolina 27848-4354, USA. jsmith@brody.med.acu.edu
Parker
A C
AC
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001439:Bacteroides / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D004265:DNA Helicases / Q000235:genetics / Q000502:physiology*; D004251:DNA Transposable Elements / Q000502:physiology*; D004269:DNA, Bacterial / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism*; D015183:Restriction Mapping; D016415:Sequence Alignment
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C083180:Mob protein, Bacteria; C095754:mobA protein, E coli; C027093:TraI protein, E coli; D004265:DNA Helicases