FIG. 2.

Mre11 has a single-stranded DNA endonuclease activity. (A) GST-Mre11 was purified from yeast by affinity chromatography of crude extracts on glutathione Sepharose. Lane M, molecular mass markers (in kilodaltons); lanes 1 and 5, uninduced soluble fraction; lanes 2 and 6, induced soluble fraction; lanes 3 and 7, unbound fraction from glutathione Sepharose; lanes 4 and 8, bound fraction from glutathione Sepharose eluted with 10 mM glutathione. (B) Endonuclease activity of Mre11. Lane M, λ DNA digested with HindIII, lane 1, φX174 viral DNA; lane 2, φX174 viral DNA with Mre11 and Mn²⁺; lane 3, pUC19 circular DNA with Mre11 and Mn²⁺; lane 4, pUC19 linear DNA with Mre11 and Mn²⁺; lane 5, φX174 viral DNA with Mre11 and Mg²⁺, φX174 viral DNA with mre11-D56N and Mn²⁺. The migration positions of molecular size markers (in kilobases) are given to the left.