DNA binding specificity of wt R.Eco29kI and mutant proteins. (a) Effect of Mg2+ ions on DNA binding by wt R.Eco29kI and R86A mutant. Lane 1, pUC128 PstI-PvuII fragments; lanes 2 and 3, reactions were carried out in the presence of Mg2+ ions; lanes 4 and 5, without Mg2+ ions. (b) Gel shift analysis of DNA binding by the mutant proteins in the presence of 5 mM EDTA. The names of the lanes are shown above the gel.