Relevance of the Srs2-Rad51 complex in the attenuation of the D-loop reaction. (A) D-loop reaction scheme. (B) In panel I, the radiolabeled D1 oligonucleotide was incubated with Rad51, Rad54, RPA (lanes 2–12) and with or without Srs2, srs2 1–998, srs2 1–910, srs2 1–875 or srs2 1–860 (7.5 or 15 nM) and then pBluescript form I DNA was incorporated. The reaction (lane 2) without Srs2 or mutant srs2 is designated as standard (Std) and corresponded to conversion of 43% of the input D1 oligonucleotide into the D-loop product. Lane 1 contained the DNA substrates but no protein. The KCl concentration was 50 mM KCl in these reactions and the results were quantified and plotted in panel II. In panel III, the results from D-loop reactions carried out at 50, 100, and 150 mM KCl with 15 nM of Srs2 or srs2 mutant were quantified and plotted. The D-loop product in the standard (Std) was 58%, 61% and 66% at 50, 100 and 150 mM KCl, respectively. (C) Panel I shows D-loop reactions with 7.5 and 15 nM Srs2, srs2 Δ875–902 or srs2 1–860 at 50 mM KCl. The D-loop in the standard (Std) was 54%. The results were quantified and plotted in panel II. In all cases, error bars represent the standard deviations derived from three independent experiments.