Induction of binding sites for RecA aptamers by differentiated-competition capillary Electrophoresis-SELEX.

The binding site-oriented SELEX strategy is an effective way to promote the functional evolution of aptamers. Here we report a novel aptamer screening strategy (Differentiated-competition Capillary Electrophoresis-SELEX), which enables candidate aptamers to be directionally induced to bind to different active sites of RecA. In this strategy, we introduce two competing binding factors into the "binding - dissociation" dynamic equilibrium system of RecA and ssDNA libraries. Due to the completely different binding mechanism of the competitive factor and the ssDNA library, it exerts different interference on the binding of RecA and the ssDNA library, which directed the binding site of aptamer candidates during the SELEX process. Multifunctional aptamers with high affinity and specificity were found to inhibit RecA activity by binding to different active sites. In conclusion, the SELEX method developed in our current study have identified a variety of biologically functional aptamers with relatively well-defined binding sites that regulate RecA protein activity, which has potential applications and future prospects for accurate screening of biological functional aptamers.