Sequence of the gene encoding a second ScrFI m super(5)C methyltransferase of Lactococcus lactis

The nucleotide (nt) sequence of a second methyltransferase (MTase)-encoding gene associated with the ScrFI restriction/modification (R/M) system (5'-CCNGG-3') of Lactococcus lactis ssp. cremoris UC503 has been determined. The coding region was 1080 nt in length and capable of specifying a 41 847-Da protein of 360 amino acids (aa). The deduced aa sequence displayed motifs characteristic of all prokaryotic 5-methylcytosine (m super(5)C) MTases. Significant similarity was observed with other m super(5)C MTases, apart from the variable region which has been deemed responsible for target sequence specificity. A larger than normal spacing between motif II and motif III, comparable in length and bearing homology to a similar region in the SssI MTase, was observed. A second open reading frame (ORF) of unknown function, which has the capacity to encode a protein of 155 aa, was observed three nt upstream from the m super(5)C MTase ORF.