Figure 3.

The polarity of strand exchange promoted by HsRad51, as determined by the fluorimetric assay. In A–D, the substrates used were those shown in Fig. 2A. (A and B) Pairing promoted by HsRad51 without and with RPA, respectively. The labels 3′ and 5′ refer to the end of the single-stranded oligonucleotide, either RG1(−) or RG2(−), at which AT-rich sequences were located. (C and D) Strand exchange promoted by HsRad51 without and with RPA, respectively. In E and F, the substrates used were those shown in Fig. 2B in which there was an alternative arrangement of the fluorescent dyes. (E) Strand exchange in the absence of RPA. (F) Strand exchange in the presence of RPA.