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 methyltransfer ase (MTase) activity was cloned and expressed in E. coil AP1-200-9 cells. T he sequence of 4681 bp was determined, and its analysis revealed two open r eading frames (ORFs) sharing some similarity with known DNA MTases. ORF1 en codes an active N4mC MTase (M.NgoMV). The enzyme modifies only one strand o f double stranded DNA and preferentially recognises the sequence GCCHR alth ough it is able to methylate other sites. The exact recognition sequence ca nnot be precisely defined due to a relaxed specificity. The second ORF show s high homology to 5mC Mtases, but we were unable to demonstrate DNA methyl ating activity of its product either in vivo or in vitro.