by Karmella Haynes, 2013
Principle: The familiar "BioBrick cloning" enzymes (i.e., EcoRI, NotI, XbaI, SpeI, PstI) are Type II restriction enzymes, which cut the sequences that they specifically bind to. The Type IIS Assembly method uses a Type IIS restriction enzyme, which binds at a specific sequence and cuts at a non-specific location exactly five base pairs away. As a result, the enzyme cleaves away its own binding site and leaves behind the most useful feature of assembly, sticky overhangs. When designed properly, Type IIS sites can be used to perform seamless assembly of parts. As an added convenience, this protocol allows cutting and ligation to occur in a single tube, as a single reaction. Thus, gel purification steps can be eliminated.
This protocol uses the Type IIS restriction enzyme BsmBI (CGTCTCn/nnnn).
- Add total volume (10.0 μL) to 50 μL chemically competent cells (e.g., BL21) in a 2.0 mL tube.
- Incubate on ice for 2 min., heat shock at 42°C for exactly 45 sec., immediately place on ice.
- Add 800 μL sterile SOC medium.
- Grow with shaking at 37°C for 30 min.
- Pellet the cells at top speed in a microcentrifuge for 3 min. at room temp.
- Discard the supernatant. Resuspend the cells in 100 μL LB + antibiotic.
- Plate cells on pre-warmed LB agar + antibiotic. Grow overnight at 37°C.
- Quick-transormation (e.g., DH5α-Turbo) is not recommended