title: Proofreading of a mutagenic nucleotide, N4-aminodeoxycytidylic acid, by Escherichia coli DNA polymerase I.
abstract: N4-Aminodeoxycytidine triphosphate, a putative metabolite of N4-aminocytidine which is a potent mutagen, is incorporated, in vitro, into polynucleotides in place of dCTP and at a much lesser extent, but significantly, in place of dTTP by E. coli DNA polymerase I large fragment. The activity of the polymerase to proofread this unnatural nucleotide has now been investigated. The results indicate that the 3'-5' exonuclease in the polymerase recognizes N4-aminocytosine as an incorrect base when N4-aminocytosine is incorporated opposite adenine but the enzyme cannot distinguish N4-aminocytosine from cytosine when it is incorporated opposite guanine.
mesh_terms: D004256:DNA Polymerase I / Q000378:metabolism*; D003845:Deoxycytosine Nucleotides / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D007700:Kinetics; D009153:Mutagens / Q000378:metabolism*; D013379:Substrate Specificity; D013698:Templates, Genetic; D014316:Tritium
chemical_list: D003845:Deoxycytosine Nucleotides; D009153:Mutagens; D014316:Tritium; C046787:N(4)-amino-2'-deoxycytidine triphosphate; D004256:DNA Polymerase I