3-methyladenine-DNA glycosylase I from Escherichia coli - Computer modeling and supporting experimental evidence

TagA (3-methyladenine-DNA glycosylase I) excises 3-methyadenine and 3-methy lguanine from alkylated DNA. The structure of this enzyme has not yet been determined experimentally. We propose a three-dimensional model of the TagA protein based on the threading algorithm. The model shows that TagA is a m ostly alpha-helical protein, in agreement with circular dichroism measureme nts. None of the eight cysteines present in the TagA sequence forms a disul fide bridge in the model structure, which has also been experimentally veri fied with the use of Ellman method. (C) 2000 Academic Press.