Exploring the DNA mimicry of the Ocr protein of phage T7

Gareth A. Roberts, Augoustinos S. Stephanou, Nisha Kanwar, Angela Dawson, Laurie P. Cooper, Kai Chen, Margaret Nutley, Alan Cooper, Garry W. Blakely, David T.F. Dryden

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

DNA mimic proteins have evolved to control DNA-binding proteins by competing with the target DNA for binding to the protein. The Ocr protein of bacteriophage T7 is the most studied DNA mimic and functions to block the DNA-binding groove of Type I DNA restriction/modification enzymes. This binding prevents the enzyme from cleaving invading phage DNA. Each 116 amino acid monomer of the Ocr dimer has an unusual amino acid composition with 34 negatively charged side chains but only 6 positively charged side chains. Extensive mutagenesis of the charges of Ocr revealed a regression of Ocr activity from wild-type activity to partial activity then to variants inactive in antirestriction but deleterious for cell viability and lastly to totally inactive variants with no deleterious effect on cell viability. Throughout the mutagenesis the Ocr mutant proteins retained their folding. Our results show that the extreme bias in charged amino acids is not necessary for antirestriction activity but that less charged variants can affect cell viability by leading to restriction proficient but modification deficient cell phenotypes.

Original languageEnglish (US)
Pages (from-to)8129-8143
Number of pages15
JournalNucleic acids research
Volume40
Issue number16
DOIs
StatePublished - Sep 2012

Bibliographical note

Funding Information:
Wellcome Trust [GR080463MA, 090288/Z/09/ZA]; RASOR grant from the BBSRC [BB/C511599/1]. Funding for open access charge: Wellcome Trust and the Biotechnology and Biological Sciences Research Council.

Fingerprint

Dive into the research topics of 'Exploring the DNA mimicry of the Ocr protein of phage T7'. Together they form a unique fingerprint.

Cite this