How does the binding exert a positive effect? How does the binding exert a positive effect? The CAP-cAMP complex triggers the formation of the DNA loop, which prevents binding of the repressor protein. The CAP-cAMP complex unbends the DNA loop, thereby allowing binding of RNA polymerase. The CAP-cAMP complex prevents the binding of the repressor protein. The CAP-cAMP complex alters the structure of the promoter and allows RNA polymerase to bind to it. Request Answer