Polypeptide composition and an immunological analysis of DNA methyltransferases from different species

The cross-reactivity of the monoclonal anti-human placental DNA methyltransferase antibody M2B10 with DNA methyltransferases isolated from other species was investigated. This antibody immunoprecipitates DNA methyltransferases from mammalian cells, i.e., human placenta, mouse P815 cells, and rat liver cells. No cross-reactivity is observed with DNA methyltransferases from wheat germ and with bacterial DNA methyltransferases HpaII and EcoRI. The mammalian enzymes are characterized by polypeptides of molecular mass 150-190 kDa. Polypeptides smaller than 190 kDa are presumably generated by proteolysis of the native 190-kDa DNA methyltransferase. Trypsin digestion of the 190-kDa polypeptide isolated from mouse cells results in progressive appearance of DNA methyltransferase polypeptides of 150-190, 110, 100, and 52-60 kDa.