Directional TOPO® cloning enables cloning of blunt-ended PCR products in a 5´→3´ orientation directly into a expression vector using a 5-minute ligation reaction, thereby eliminating subcloning steps and saving you time.

Directional TOPO® cloning vectors contain a single-strand GTGG overhang on the 5´ end and a blunt end on the 3´ end. The four-nucleotide overhang invades the double-strand DNA of the PCR product and anneals to the CACC sequence that you place in your 5´ primer. Topoisomerase I then ligates the PCR product in the correct orientation.

With Directional TOPO® Cloning Expression Kits, you will:

  • Save time - TOPO® cloning of your PCR product takes just five minutes
  • Obtain efficient cloning results - recombinant clones (>90%) will be in the correct orientation for expression (Figure 1)
  • Achieve high-level expression - vectors carry powerful promoters for expression in E coli or mammalian cells

Figure 1: Directional cloning of human open reading frames into pcDNA® 3.1 D/VS- His- TOPO® vector.

TOPO® bacterial expression