Abstract
The structured core of the N-terminal 3′–5′ exonuclease domain of ϵ, the proofreading subunit of Escherichia coli DNA polymerase III, was defined by multidimensional NMR experiments with uniformly 15N-labeled protein: it comprises residues between Ile-4 and Gln-181. A 185-residue fragment, termed ϵ(1–185), was crystallized by the hanging drop vapor diffusion method in the presence of thymidine-5′-monophosphate, a product inhibitor, and Mn2+ at pH 5.8. The crystals are tetragonal, with typical dimensions 0.2 mm × 0.2 mm × 1.0 mm, grow over about 2 weeks at 4°C, and diffract X-rays to 2.0 Å. The space group was determined to be P4n212 (n = 0, 1, 2, 3), with unit cell dimensions a = 60.8 Å, c = 111.4 Å.