Fig. 1.

Superposition of two 12-bp B-DNA molecules on the ocr dimer.⁵ Ocr is shown in blue ribbon form, with the N- and C-termini indicated and the dimer interface shown as a red line. A fit of phosphate groups of a B-DNA complex onto 12 carboxyl groups of ocr gave an rms fit of 1.9 Å. Phosphate groups are shown in yellow (phosphorus) and purple (oxygen). The carboxyl groups are shown in red (oxygen) and black (carbon). The sugar backbones of the DNA chains are shown in two shades of green with the base pairs omitted for clarity. Vectors for the DNA helical axes are drawn as black lines.