Abstract: Conformationally-constrained helicases having improved activity and strength are provided. Methods of making conformationally-constrained helicases having improved activity and strength are provided. Methods of using conformationally-constrained helicases having improved activity and strength are provided. The present invention is based on the discovery of novel modified helicases that show dramatically enhanced helicase activity and increased strength as compared to unmodified helicases. As described further herein, it has been surprisingly discovered that, by controlling the conformation of certain subdomains such that the helicase remains in a closed form (e.g.