[Isolation, purification and properties of restrictase and methylase BstN1 from Bacillus stearothermophilus]

Restriction-methylation enzymes BstN1 from Bacillus stearothermophilus were isolated and purified. These enzymes are related to a new class of restriction-methylation enzymes of the second type, whose modifying component is N4-cytosine-DNA-methylase. Both enzymes recognize the DNA sequence CC(A/T)GG. Restrictase BstN1 is a protein made up of one subunit with a molecular mass of 25 kDa. The molecular mass of native DNA-methylase BstN1 is about 55 kDa. The temperature optima for restrictase and methylase BstN1 are around 60 degrees C. Possible uses of BstN1 restriction-methylation enzymes for the analysis of cytosine methylation in bacterial and higher plant DNA are discussed.