Cloning and characterization of Sse9I DNA-methyltransferase recognizing 5'-AATT-3'.

The gene from Sporosarcina species 9D encoding Sse9I DNA-methyltransferase (M.Sse9I) was cloned and expressed in Escherichia coli. The recombinant plasmid pMSse-1 contains the M.Sse9I gene 1086 bp in length, corresponding to a protein of 362 amino acid residues. M.Sse9I recognizes the tetranucleotide sequence 5'-AATT-3' and modifies the second adenine within the recognition sequence. The amino acid sequence of M.Sse9I was compared with those of other methylases. According to mutual positions of four conservative domains the new enzyme belongs to a subgroup of D12 class. This subgroup includes Sse9I, CviAII, NlaIII and N-terminal domains of LlaI, FokI and StsI DNA-methyltransferases.