THE DNA ADENINE METHYLTRANSFERASE-ENCODING GENE (DAM) OF VIBRIO-CHOLERAE

The DNA adenine methyltransferase (MTase)-encoding gene (dam) of Vibri o cholerae, an organism belonging to the family Vibrionaceae, has been cloned and the complete nucleotide (nt) sequence determined. V. chole rae dam encodes a 21.5-kDa protein and is directly involved in methyl- directed DNA mismatch repair. It can substitute for the Escherichia co li enzyme and can suppress the phenotypic traits associated with E. co li dam mutants. Overproduction of V. cholerae Dam MTase does not resul t in hypermutability in either V. cholerae or E. coli cells. Overprodu ction of V. cholerae Dam in a pUC plasmid, however, fails to suppress the 2-aminopurine (2-AP)-sensitive phenotype of E. coli dam mutants. H omology between the nt and deduced amino acid (aa) sequences of the E. coli and V. cholerae dam genes is only 30-35%.