Figure 1.

DNA strand exchange in trans. A RecA nucleoprotein filament is assembled on ssDNA in the presence of ATPγS (A). This filament is introduced to heterologous dsDNA to form a nonhomologously bound complex (B). To probe the receptiveness of the bound dsDNA, exogenous ³²P-labeled ssDNA that is complementary to this dsDNA is added to the complex (C). DNA strand exchange in trans between homologous ³²P-labeled ssDNA and the unlabeled dsDNA results in ³²P-labeled dsDNA and unlabeled ssDNA products.