Table 1.
Type IIB restriction–modification systems
| Enzyme | Source organism | Recognition sequencea | Excised fragmentb (bp) | No. peptidesc (and proposed ratio) | Nuclease requirement for AdoMet | Reference |
|---|---|---|---|---|---|---|
| AlfI | Acinetobacter lwoffi BH 32 | (10/12) GCA-N6-TGC (12/10) | 34 | – | Yes | 3 |
| AloI | Acinetobacter lwoffi Ks 4–8 | (7/12) GAAC-N6-TCC (12/7)V | 32 | 1 | No | 47 |
| BaeI | Bacillus sphaericus | (10/15) AC-N4-GTAYC (12/7)V | 33 | 2 (−) | Yes | 49 |
| BcgI | Bacillus coagulans | (10/12) CGA-N6-TGC (12/10) | 34 | 2 (A2B1) | Yes | 41–43 |
| BplI | Bacillus pumilus | (8/13) GAG-N5-CTC (13/8) | 32 | 2 (A1B1) | Yes | 50 |
| BsaXI | Bacillus stearothermophilus | (9/12) AC-N5-CTCC (10/7) | 30 | – | No | 3 |
| CspCI | Citrobacter species 2144 | (11/13) CAA-N5-GTGG (12/10)V | 35 | – | Yes | 3 |
| FalI | Flavobacterium aquatile | (8/13) AAG-N5-CTT (13/8) | 32 | – | Yes | 3 |
| PpiI | Pseudomonas putida | (7/12) GAAC-N5-CTC (13/8)V | 32 | 1 | No | 48 |
| PsrI | Pseudomonas stutzeri | (7/12) GAAC-N6-TAC (12/7) | 32 | – | No | 3 |
All of the Type IIB restriction endonucleases analysed here are listed, with the bacterial species from which they were originally isolated.
In the recognition sequences, the pairs of numbers either side of the nucleotide sequence shown indicate the number of bases between the specified sequence and the point of cleavage, firstly in the strand shown, secondly in the complementary strand. N denotes any base and Y a pyrimidine.
The length of the DNA fragment that the nuclease excises from its substrate is given as the number of bases in each strand.
Whenever known (– indicates not known), the number of different polypeptide chains is as shown: for two-polypeptide systems, the ratio is given.
Indicates that these particular enzymes can cleave at varied positions that differ from the canonical by 1 or 2 bp.