Structural characterization of two tandemly arranged DNA methyltransferasegenes from Neisseria gonorrhoeae MS11: N4-cytosine specific M.NgoMXV and nonfunctional 5-cytosine-type M.NgoMorf2P

Two adjacent genes encoding DNA methyltransferases (MTases) of Neisseria go norrhoeae MS11, an active N4-cytosine specific M. NgoMXV and an inactive 5- cytosine type M, NgoMorf2P, were cloned into Escherichia coli and sequenced . We analyzed the deduced amino acid sequence-of both gene products and loc alized conserved regions characteristic for DNAMTases, Structure prediction , threading-derived alignments, and comparison with the common fold for DNA MTases allowed for construction of super-secondary and tertiary models for M.NgoMorf2P and M.NgoMXV, respectively. These models helped in identificat ion of amino acids and structural elements essential for function of both e nzymes. The implications of this putative structural model on the catalytic mechanism of M.NgoMXV and its possible relation to the common ancestor of modern DNA amino-MTases are also discussed. Proteins 1999;37:717-728. (C) 1 999 Wiley-Liss, Inc.