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Updated: Aug 17, 2026

Analyzing and Building Nucleic Acid Structures with 3DNA
Published on: April 26, 2013
Structure of Ocr from bacteriophage T7, a protein that mimics B-form DNA
M D Walkinshaw1, P Taylor, S S Sturrock
1Institute of Cell and Molecular Biology, The King's Buildings, University of Edinburgh, EH9 3JR, Edinburgh, United Kingdom. malcolm.walkinsahaw@ed.ac.uk
Abstract:
We have solved, by X-ray crystallography to a resolution of 1.8 A, the structure of a protein capable of mimicking approximately 20 base pairs of B-form DNA. This ocr protein, encoded by gene 0.3 of bacteriophage T7, mimics the size and shape of a bent DNA molecule and the arrangement of negative charges along the phosphate backbone of B-form DNA. We also demonstrate that ocr is an efficient inhibitor in vivo of all known families of the complex type I DNA restriction enzymes. Using atomic force microscopy, we have also observed that type I enzymes induce a bend in DNA of similar magnitude to the bend in the ocr molecule. This first structure of an antirestriction protein demonstrates the construction of structural mimetics of long segments of B-form DNA.
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