StyD4I restriction-modification system of Salmonella typhi D4: cloning and sequence analysis.

A plasmid (5.4 kbp) from Salmonella Typhi D4 has been identified as encoding a restriction and modification (R-M) system. DNA fragments (2537 bp) that carried the genes for restriction endonuclease and methyltransferase encoded on the plasmid were sequenced. Two divergently arranged open reading frames of 957 bp for the restriction endonuclease consisting of 318 aa (amino acids) and 1140 bp for the DNA methyltransferase consisting of 379 aa were identified. These sequences were similar to the sequences of the SsoII R-M system, including the interspace between the two genes.