The Orf18 gene product from conjugative transposon Tn916 is an ArdA antirestriction protein that inhibits type I DNA restriction-modification systems.
Gene orf18, which is situated within the intercellular transposition region of the conjugative transposon Tn916 from the bacterial pathogen Enterococcus faecalis, encodes a putative ArdA (alleviation of restriction of DNA A) protein. Conjugative transposons are generally resistant to DNA restriction upon transfer to a new host. ArdA from Tn916 may be responsible for the apparent immunity of the transposon to DNA restriction and modification (R/M) systems and for ensuring that the transposon has a broad host range. The orf18 gene was engineered for overexpression in Escherichia coli, and the recombinant ArdA protein was purified to homogeneity. The protein appears to exist as a dimer at nanomolar concentrations but can form larger assemblies at micromolar concentrations. R/M assays revealed that ArdA can efficiently inhibit R/M by all four major classes of Type I R/M enzymes both in vivo and in vitro. These R/M systems are present in over 50% of sequenced prokaryotic genomes. Our results suggest that ArdA can overcome the restriction barrier following conjugation and so helps increase the spread of antibiotic resistance genes by horizontal gene transfer.
Serfiotis-Mitsa
Dimitra
D
School of Chemistry, The University of Edinburgh, The King's Buildings, Edinburgh EH9 3JJ, UK.
Roberts
Gareth A
GA
Cooper
Laurie P
LP
White
John H
JH
Nutley
Margaret
M
Cooper
Alan
A
Blakely
Garry W
GW
Dryden
David T F
DT
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001667:Binding, Competitive; D002152:Calorimetry, Differential Scanning; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002876:Chromosomes, Bacterial / Q000378:metabolism; D015280:DNA Restriction-Modification Enzymes / Q000037:antagonists & inhibitors*; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D013293:Enterococcus faecalis / Q000378:metabolism*; D008970:Molecular Weight; D016366:Open Reading Frames / Q000235:genetics; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000378:metabolism; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000037:antagonists & inhibitors; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
D001426:Bacterial Proteins; D015280:DNA Restriction-Modification Enzymes; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D011994:Recombinant Proteins; C093244:DNA modification methylase EcoKI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)