Systematic variation in DNA length yields highly ordered repressor-operator cocrystals

Abstract

Crystals have been grown that contain the operator-binding domain of the λ repressor and the operator site OL1. Crystallization conditions were tested with a set of DNA fragments, ranging in length from 17 to 23 base pairs. The best crystals were grown with a 20-base pair DNAfragment. These crystals have spacegroup symmetry P21, with unit cell dimensions a = 37.1 Å, b = 68.8 Å, c = 56.8 Å, and a β angle of 91.5°. They diffracted to at least 2.5 Å resolution. High resolution data from these crystals should allow the direct determination of how a repressor recognizes its operator site.