 However, an "in vitro" kinetic analysis of RNAi in the presence and absence of ATP showed that ATP may be required to unwind and remove the cleaved mRNA strand from the RISC complex after catalysis.The guide strand tends to be the one whose 5' end is less stably paired to its complement, but strand selection is unaffected by the direction in which dicer cleaves the dsRNA before RISC incorporation.Instead, the R2D2 protein may serve as the differentiating factor by binding the more-stable 5' end of the passenger strand.