N(6)-Adenine DNA-methyltransferase in Wheat Seedlings

The N(6)-adenine DNA-methyltransferase was isolated from the vacuolar vesicle fraction of wheat coleoptiles. In the presence of S-adenosyl-L-methionine the enzyme de novo methylates the first adenine residue in the TGATCA sequence in the single- or double-stranded DNA substrates but it prefers single-stranded structures. Wheat adenine DNA-methyltransferase (wadmtase) is a Mg(2+)- or Ca(2+)-dependent enzyme with a maximum activity at pH 7.5-8.0. Wadmtase seems to be responsible for mitochondrial DNA modification that might be involved in the regulation of replication of mitochondria in plants.