Purification of a DNA methyltransferase from Bacillus natto B3364.

An S-adenosyl-L-methionine:DNA-methyltransferase, termed M.BnaI, was purified from Bacillus natto B3364 strain by successive column chromatography. The molecular weight determined by gel filtration was 37 kDa for M.BnaI. Analysis of methyltransferase by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed correspondence of the M.BnaI activity with one protein band at a molecular weight of 35 kDa. Sequencing of pUC19 DNA methylated with M.BnaI showed the cytosine-5 methylation in the BnaI recognition sequence GGAT decreases CC at the position indicated by the arrow.