title: A mutational analysis of DNA mimicry by ocr, the gene 0.3 antirestriction protein of bacteriophage T7.
abstract: 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.
authors.affiliation: EaStChem School of Chemistry, The University of Edinburgh, The King's Buildings, Edinburgh EH9 3JJ, UK.
authors.forename: Augoustinos S
authors.initials: AS
authors.lastname: Stephanou
authors.forename: Gareth A
authors.initials: GA
authors.lastname: Roberts
authors.forename: Mark R
authors.initials: MR
authors.lastname: Tock
authors.forename: Emily H
authors.initials: EH
authors.lastname: Pritchard
authors.forename: Rachel
authors.initials: R
authors.lastname: Turkington
authors.forename: Margaret
authors.initials: M
authors.lastname: Nutley
authors.forename: Alan
authors.initials: A
authors.lastname: Cooper
authors.forename: David T F
authors.initials: DT
authors.lastname: Dryden
mesh_terms: 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
chemical_list: C440255:Ocr protein, bacteriophage T7; D014764:Viral Proteins; D004262:DNA Restriction Enzymes