TABLE 1.
DNA methyltransferases in E. coli K-12
| Gene(s) | Modification methyltransferase | Recognition sequencea | Number in genomeb | Restriction endonucleasesc |
|---|---|---|---|---|
| hsdSM | M.EcoK | -AAC(N6)GTCG- | 595 | EcoKI |
| dam | Dam | -GATC- | 19,120 | DpnI, DpnII, Sau3A |
| dcm | Dcm | -CCWGG- | 12,045 | EcoRII, BstNI |
| yhdJ | YhdJ | -ATGCAT- | 839 | NsiI |
a
The base in boldface is modified.
b
All M.EcoK sites are methylated. For Dam and Dcm, most sites are methylated but this number also includes hemimethylated and unmethylated sites. YhdJ methylation is below the limit of detection at this sequence.
c
Restriction enzymes recognize the same sequence as the methyltransferases. EcoKI cuts only if the sequence is unmethylated; DpnI cleaves only if the sequence is methylated; Sau3A cuts regardless of the state of methylation. EcoRII cleaves only at unmethylated sites and BstNI cutting is not affected by methylation.