The Flexi® Vector Systems use two rare-cutting restriction enzymes, SgfI and PmeI, in a simple, yet powerful, directional cloning method for protein-coding sequences. These systems provide a rapid, efficient and high-fidelity way to transfer these sequences between a variety of Flexi® Vectors. The Flexi® Vectors contain various expression or peptide tag options to enable expression of native or fusion proteins to study protein structure and function, as well as protein-protein interactions. All Flexi® Vectors carry the lethal barnase gene, which is replaced by the DNA fragment of interest and acts as a positive selection for successful ligation of the insert.