Cloning and characterization of the gene encoding a new DNA methyltransferase from Neisseria gonorrhoeae.

A HindIII fragment of N. gonorrhoeae MS11 DNA coding for DNA methyltransferase (MTase) activity was cloned and expressed in E. coli AP1-200-9 cells. The sequence of 4681 bp was determined, and its analysis revealed two open reading frames (ORFs) sharing some similarity with known DNA MTases. ORF1 encodes an active N4mC MTase (M.NgoMV). The enzyme modifies only one strand of double stranded DNA and preferentially recognises the sequence GCCHR although it is able to methylate other sites. The exact recognition sequence cannot be precisely defined due to a relaxed specificity. The second ORF shows high homology to 5mC Mtases, but we were unable to demonstrate DNA methylating activity of its product either in vivo or in vitro.