Investigation of restriction-modification enzymes from M. varians RFL19 with a new type of specificity toward modification of substrate.
The characterization of MvaI restriction-modification enzymes, isolated from Micrococcus varians RFL19, is reported. Both enzymes recognize the 5'CC decreases (A/T)GG nucleotide sequence. The endonuclease cleaves the sequence at the position indicated by the arrow, whereas the methylase modifies the internal cytosine, yielding N4-methylcytosine. This type of modification protects the substrate from R.MvaI cleavage. 5-Methylcytosine in the same position of the recognition sequence does not protect the substrate from R.MvaI cleavage. R.MvaI proved to be the first example of a restriction endonuclease differentiating the position of the methyl group in the heterocyclic ring of cytosine, located in the same site of the recognition sequence. M.MvaI modifies DNA dcm+ in vitro yielding N4,5-dimethylcytosine. N4-methylcytosine cannot be differentiated from cytosine using the Maxam-Gilbert DNA sequencing procedure.
Butkus
V
V
Klimasauskas
S
S
Kersulyte
D
D
Vaitkevicius
D
D
Lebionka
A
A
Janulaitis
A
A
D044503:5-Methylcytosine; D001483:Base Sequence; D003596:Cytosine / Q000031:analogs & derivatives / Q000032:analysis; D004247:DNA; D004262:DNA Restriction Enzymes / Q000302:isolation & purification / Q000378:metabolism*; D015252:Deoxyribonucleases, Type II Site-Specific; D007700:Kinetics; D008745:Methylation; D008837:Micrococcus / Q000201:enzymology*; D013379:Substrate Specificity
D044503:5-Methylcytosine; D003596:Cytosine; D004247:DNA; D004262:DNA Restriction Enzymes; C046545:CCWGG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific