Properties of 3-methyladenine-DNA glycosylase from Escherichia coli

Publisher Website
Google Scholar
Abstract
An E. coli enzyme that releases 3-methyladenine and 3-ethyladenine in free form from alkylated DNA was purified 2800-fold in 7% yield. The enzyme does not liberate several other alkylation products from DNA, including 7-methylguanine, O6-methylguanine, 7-methyladenine, N6 methyladenine, 7-ethylguanine, O6-ethylguanine and the arylalkylated purine derivatives obtained by treatment of DNA with 7-bromomethyl-12-methylbenz[a]anthracene. The reaction of the enzyme with alkylated DNA leads to the introduction of apurinic sites but no chain breaks (less than 1 incision/10 apurinic sites), and there is no detectable nuclease activity with native DNA, depurinated DNA, UV-irradiated DNA or X-irradiated DNA as potential substrates. The enzyme is termed 3-methyladenine-DNA glycosylase. It is a small protein, MW = 19,000, that does not require divalent metal ions, phosphate or other cofactors in order to cleave base-sugar bonds in alkylated DNA.