A mutational analysis of DNA mimicry by ocr, the gene 0.3 antirestriction protein of bacteriophage T7.
The ocr protein of bacteriophage T7 is a structural and electrostatic mimic of approximately 24 base pairs of double-stranded B-form DNA. As such, it inhibits all Type I restriction and modification (R/M) enzymes by blocking their DNA binding grooves and inactivates them. This allows the infection of the bacterial cell by T7 to proceed unhindered by the action of the R/M defence system. We have mutated aspartate and glutamate residues on the surface of ocr to investigate their contribution to the tight binding between the EcoKI Type I R/M enzyme and ocr. Contrary to expectations, all of the single and double site mutations of ocr constructed were active as anti-R/M proteins in vivo and in vitro indicating that the mimicry of DNA by ocr is very resistant to change.
Stephanou
Augoustinos S
AS
EaStChem School of Chemistry, The University of Edinburgh, The King's Buildings, Edinburgh EH9 3JJ, UK.
Roberts
Gareth A
GA
Tock
Mark R
MR
Pritchard
Emily H
EH
Turkington
Rachel
R
Nutley
Margaret
M
Cooper
Alan
A
Dryden
David T F
DT
D000595:Amino Acid Sequence; D017123:Bacteriophage T7 / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004262:DNA Restriction Enzymes / Q000037:antagonists & inhibitors; D019281:Dimerization; D004926:Escherichia coli / Q000821:virology; D018716:Molecular Mimicry / Q000235:genetics*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics
C440255:Ocr protein, bacteriophage T7; D014764:Viral Proteins; D004262:DNA Restriction Enzymes