Flexi® Cloning System

The Flexi® Vector System is a directional cloning method for protein-coding sequences.


The Flexi® Vector System is a directional cloning method for protein-coding sequences. It is based on two rare-cutting restriction enzymes, SgfI and PmeI, and provides a rapid, efficient and high-fidelity way to transfer protein-coding regions without the need to resequence. Once an ORF is cloned, conveniently transfer the inserts into a variety of vectors designed for multiple applications. No licensing fees or complicated transfer restrictions needed.

All Flexi® Vectors carry the lethal barnase gene, which is replaced by the DNA fragment of interest and acts as a positive selection for the successful ligation of the insert.

Unlike site-specific recombination vector systems, the Flexi® Vector Systems do not require appending multiple amino acids to the amino or carboxy termini of the protein of interest. In addition, the systems do not require an archival entry vector, and most applications allow direct entry into the vector suited to the experimental design.

C-terminal Flexi® Vectors allow expression of C-terminal-tagged proteins. While these vectors can act as acceptors of protein-coding regions flanked by SgfI and PmeI, they lack a PmeI site and contain a different blunt-ended site, EcoICRI. This joined sequence cannot be removed from the C-terminal Flexi® Vectors and transferred to other Flexi® Vectors.

Features – Benefits

  • Choose from a variety of initial applications (e.g., bacterial protein, mammalian or cell-free protein expression) and then transfer the insert as required
  • Efficient insert transfer means direct use of recombinant clones with minimal time for screening background colonies
  • Adaptable to high-throughput formats for large screening projects
Kit Size Brand Catalog
Entry/Transfer 5 entry & 20 transfer reactions Promega C8640
Transfer, C terminal 50 transfer reactions Promega C9320
Transfer, N terminal 100 transfer reactions Promega C8820