Type IIs Restriction Endonuclease

Restriction enzymes can be divided into four categories according to their different enzyme digestion methods, named Type I, Type II, Type III and Type IV. Our commonly used restriction endonucleases, such as EcoRI, belong to type II restriction endonucleases, which recognize specific 4 to 8 nucleotide sequences . The recognized sequence is inverted repeats and the cleavage site is located in the recognition site. After enzymatic cleavage and the cleavage end or blunt end is produced. The cutting diagram is as follows:

R II

R IIs

However, compared with the common Type II restriction enzymes the Type IIS restriction endonuclease is a relatively specific enzyme that cleaves DNA downstream of the recognition site, from the three-dimensional structure analysis of the enzyme. This is due to the fact that the recognition and catalytic regions of the Type IIS restriction enzyme are separated by a polypeptide linker.

The advantage of the TypeII S restriction enzyme is that it has no requirement to a cleavage sequence. The cutting position can be any sequence, and multiple DNA fragments can be assembled through complementary ends. This assembly method is also called GoldenGate Assembly.